Directional Distribution Research Articles

Meningkatkan Karakter Gotong Royong Peserta Didik dalam Pembelajaran PAKBP dengan Model PBL Fase C Kelas V di SDN 23 Periang

This research aims to describe the extent to which the application of the Problem Based Learning (PBL) model in PAKBP subjects can improve the mutual cooperation character of class V Phase C students at SDN 23 Periang, Kayan Hilir District, Sintang Regency. This type of research is Classroom Action Research (PTK), with two cycles, namely cycle 1 and cycle 2. The activity stages are planning, implementation, observation, analysis and reflection which are carried out face to face. The research is entitled "Improving Students' Mutual Cooperation Character in PAKBP Learning Using the PBL Phase C Model for Class V at SDN 23 Periang." The research was carried out at SDN 23 Periang from 13 to 20 September 2024. The research subjects were students in class 5 Phase C. The object of the research was the application of the Problem Based Learning (PBL) model in improving the mutual cooperation character of students in class V Phase C. Data collection was carried out by means of direct observation and distribution of questionnaires. Data analysis techniques: data collection, data condensation, presentation and drawing conclusions. The research results show that the PBL model can be an effective approach in developing students' cooperative character. The results of the research also show that there is a significant increase in the mutual cooperation character of students, and is able to encourage the growth of an attitude of mutual cooperation. Through group activities and structured discussions, students are trained to respect each other's differences of opinion, share responsibility, share information and collaborate to achieve common goals. .

Global-scale gravity wave analysis methodology for the ESA Earth Explorer 11 candidate CAIRT

Abstract. In the past, satellite climatologies of gravity waves (GWs) have initiated progress in their representation in global models. However, these could not provide the phase speed and direction distributions needed for a better understanding of the interaction between GWs and the large-scale winds directly. The ESA Earth Explorer 11 candidate CAIRT could provide such observations. CAIRT would use a limb-imaging Michelson interferometer resolving a wide spectral range, allowing temperature and trace gas mixing ratio measurements. With the proposed instrument design, a vertical resolution of 1 km, along-track sampling of 50 km, and across-track sampling of 25 km in a 400 km wide swath will be achieved. In particular, this allows for the observation of three-dimensional (3D), GW-resolving temperature fields throughout the middle atmosphere. In this work, we present the methodology for the GW analysis of CAIRT observations using a limited-volume 3D sinusoidal fit (S3D) wave analysis technique. We assess the capability of CAIRT to provide high-quality GW fields by the generation of synthetic satellite observations from high-resolution model data and comparison of the synthetic observations to the original model fields. For the assessment, wavelength spectra, phase speed spectra, horizontal distributions, and zonal means of GW momentum flux (GWMF) are considered. The atmospheric events we use to exemplify the capabilities of CAIRT are the 2006 sudden stratospheric warming (SSW) event, the quasi-biennial oscillation (QBO) in the tropics, and the mesospheric preconditioning phase of the 2019 SSW event. Our findings indicate that CAIRT would provide highly reliable observations not only of global-scale GW distributions and drag patterns but also of specific wave events and their associated wave parameters. Even under worse-than-expected noise levels of the instrument, the resulting GW measurements are highly consistent with the original model data. Furthermore, we demonstrate that the estimated GW parameters can be used for ray tracing, which physically extends the horizontal coverage of the observations beyond the orbit tracks.

Direct Channel or Distribution Channel? The Role of Internet-Based Targeted Advertising With Vertical Differentiation in Distinct Channels

The selection of optimal channels is considered the critical marketing strategy for the firm. Effective vertical channel selection could induce distinct effects on the firm’s profit and social warfare by selecting a specific type of advertising. Otherwise, as the targeted population is quite different for the firm using mass or targeted advertising, this differentiation is becoming more significant for the population in the final marketing channel. Within the vertical differentiation model, the role of Internet-based targeted advertising on direct sales and distribution channels is studied. Compared to mass advertising, the firm using Internet-based targeted advertising in distinct channels can benefit the firm’s equilibrium profit by reducing advertising waste and enhancing the product’s price. The manufacturer might use Internet-based targeted advertising to control the total profit of the channel. Meanwhile, Internet-based targeted advertising might reduce the retailer’s and the entire channel’s profit. Otherwise, the targeting accuracy of the firm shows a bidirectional role in the firm’s equilibrium price in the direct channel. The firm’s equilibrium advertising level and profit might be reduced with the increasing targeting accuracy. The public department of the government needs to consider the potential risk of targeted advertising that might reduce the real benefits of distribution channels and harm the development of the market.

Enrichment conditions and resource potential of coal-rock gas in Ordos Basin, NW China

To reveal the enrichment conditions and resource potential of coal-rock gas in the Ordos Basin, this paper presents a systematic research on the sedimentary environment, distribution, physical properties, reservoir characteristics, gas-bearing characteristics and gas accumulation play of deep coals. The results show that thick coals are widely distributed in the Carboniferous–Permian of the Ordos Basin. The main coal seams Carboniferous 5# and Permian 8# in the Carboniferous–Permian have strong hydrocarbon generation capacity and high thermal evolution degree, which provide abundant materials for the formation of coal-rock gas. Deep coal reservoirs have good physical properties, especially porosity and permeability. Coal seams Carboniferous 5# and Permian 8# exhibit the average porosity of 4.1% and 6.4%, and the average permeability of 8.7×10−3 μm2 and 15.7×10−3 μm2, respectively. Cleats and fissures are developed in the coals, and together with the micropores, constitute the main storage space. With the increase of evolution degree, the micropore volume tends to increase. The development degree of cleats and fissures has a great impact on permeability. The coal reservoirs and their industrial compositions exhibit significantly heterogeneous distribution in the vertical direction. The bright coal seam, which is in the middle and upper section, less affected by ash filling compared with the lower section, and contains well-developed pores and fissures, is a high-quality reservoir interval. The deep coals present good gas-bearing characteristics in Ordos Basin, with the gas content of 7.5–20.0 m3/t, and the proportion of free gas (greater than 10%, mostly 11.0%–55.1%) in coal-rock gas significantly higher than that in shallow coals. The enrichment degree of free gas in deep coals is controlled by the number of macropores and microfractures. The coal rock pressure testing shows that the coal-limestone and coal-mudstone combinations for gas accumulation have good sealing capacity, and the mudstone/limestone (roof)-coal-mudstone (floor) combination generally indicates high coal-rock gas values. The coal-rock gas resources in the Ordos Basin were preliminarily estimated by the volume method to be 22.38×1012 m3, and the main coal-rock gas prospects in the Ordos Basin were defined. In the central-east of the Ordos Basin, Wushenqi, Hengshan–Suide, Yan'an, Zichang, and Yichuan are coal-rock gas prospects for the coal seam #8 of the Benxi Formation, and Linxian West, Mizhi, Yichuan–Huangling, Yulin, and Wushenqi–Hengshan are coal-rock gas prospects for the coal seam #5 of the Shanxi Formation, which are expected to become new areas for increased gas reserves and production.

Borehole Stability of Natural Gas Hydrate Reservoirs

Abstract The decomposition of natural gas hydrate (NGH) due to long-term drilling may decrease the strength of reservoirs and increase the borehole failure risk. Meanwhile, the creep properties of NGH reservoirs also may give rise to engineering problems including borehole shrinkage and jamming of drilling tools in the late stage of drilling, which seriously impairs the drilling safety. A thermal-fluid-solid multi-field coupling model considering the decomposition kinetics of NGH and creep properties of reservoirs was established to explore the influence mechanism of NGH decomposition and creep properties of hydrate-bearing sediments on mechanical behaviors of boreholes. In addition, influences of drilling parameters and geomechanical properties of reservoirs on borehole stability in the drilling process of NGH reservoirs were analyzed. Research results show that creep properties of NGH deposits causes homogenization of stress distribution in different directions of NGH reservoirs around boreholes, transition of plastic zones around boreholes to a round shape, and possibly overall borehole collapse. As the horizontal geostress becomes more inhomogeneous, the borehole instability risk increases; the higher the initial pore pressure of formation is, the lower the effective geostress and the lower the borehole instability risk. The research results can provide theoretical support for safe drilling of NGH reservoirs in South China Sea and promote the early commercial exploitation of NGH resources in China.

Wavelet-Inspired Multi-Channel Score-Based Model for Limited-Angle CT Reconstruction.

Score-based generative model (SGM) has demonstrated great potential in the challenging limited-angle CT (LA-CT) reconstruction. SGM essentially models the probability density of the ground truth data and generates reconstruction results by sampling from it. Nevertheless, direct application of the existing SGM methods to LA-CT suffers multiple limitations. Firstly, the directional distribution of the artifacts attributing to the missing angles is ignored. Secondly, the different distribution properties of the artifacts in different frequency components have not been fully explored. These drawbacks would inevitably degrade the estimation of the probability density and the reconstruction results. After an in-depth analysis of these factors, this paper proposes a Wavelet-Inspired Score-based Model (WISM) for LA-CT reconstruction. Specifically, besides training a typical SGM with the original images, the proposed method additionally performs the wavelet transform and models the probability density in each wavelet component with an extra SGM. The wavelet components preserve the spatial correspondence with the original image while performing frequency decomposition, thereby keeping the directional property of the artifacts for further analysis. On the other hand, different wavelet components possess more specific contents of the original image in different frequency ranges, simplifying the probability density modeling by decomposing the overall density into component-wise ones. The resulting two SGMs in the image-domain and wavelet-domain are integrated into a unified sampling process under the guidance of the observation data, jointly generating high-quality and consistent LA-CT reconstructions. The experimental evaluation on various datasets consistently verifies the superior performance of the proposed method over the competing method.

Pengaruh Keterampilan Wirausaha dan Motivasi Berwirausaha terhadap Keberhasilan Usaha

MSME entrepreneurship is one aspect of local economic development while contributing to the employment network in Medan city. With the existence of MSMEs, they are able to contribute to regional economic development and reduce unemployment. However, in the process of running a business, there are obstacles for entrepreneurs, namely the lack of entrepreneurial skills and lack of motivation in entrepreneurship which can affect the success of MSMEs. This study aims to determine the effect of entrepreneurial skills and entrepreneurial motivation on business success in MSMEs in Medan city. The form of research used is quantitative with an associative approach. The population in this study were MSMEs in Medan City. With a sample of 100 respondents, the sample approach used in this study was non-probability sampling in the form of purposive sampling. Primary data obtained through direct distribution of questionnaires and secondary data obtained through literature studies. The results of this study indicate that entrepreneurial skills have a significant positive effect on business success, obtained a tcount value of 4.420> 1.984 with a sig value of 0.001 <0.05 and has a regression coefficient value of 0.325. Entrepreneurial motivation also has a significant positive effect on business success, obtained a tcount value of 2.680> 1.984 with a sig value of 0.009 <0.05 and has a regression coefficient value of 0.235. In simultaneous testing of entrepreneurial skills and entrepreneurial motivation variables simultaneously affect the level of influence of 49.7% while the remaining 50.3% is influenced by factors outside this study.

Distribution Activities At The Sungai Lulut Traditional Market As A Source of Learning Social Studies

The Sungai Lulut traditional market is a market in the Banjar Regency area, specifically in the Sungai Lulut sub-district. In this market there are economic activities that can be used as a learning resource. The learning process cannot be separated from the learning resources used. One of several learning sources that can be used is the environment. With regard to the environment, there is economic activity from the distribution around students that can be used as a learning resource in social studies learning. Learning resources that utilize existing economic activities in the market are still not optimally used by teachers because there are obstacles such as limited time, remote locations and inadequate facilities, even though they are very effective if used as learning resources. This research aims to describe the economic activities of distribution activities in the Sungai Lulut traditional market as a social studies learning resource. The approach used in this research is qualitative with descriptive methods. Data collection techniques through observation, interviews and documentation. Data analysis through data reduction, data presentation, and data verification. The data validity test used is triangulation of sources, techniques and time. The research results show that distribution activities in the Sungai Lulut traditional market are through direct and indirect distribution. Direct distribution, for example, risol traders and food stalls in the Sungai Lulut traditional market. This distribution activity is suitable for social studies learning as a learning resource for economic activity material, namely production, distribution and consumption at the even seventh semester grade junior high school level.

Myogenic response of the cerebral vessel: a mathematical model

The myogenic response is most typical for small arterial vessels and consists in constriction of the vessel with an increase in transmural pressure, the pressure difference between the inner and outer surfaces of the vascular wall. There are many models describing this response. In models of last decades, in addition to macrostretchings and macrostrains, their microanalogues are introduced into consideration, that significantly complicates the description. In the presented work a simple model of the wall of the small cerebral artery is described, which includes the main parameters that control the myogenic response and corresponds to physiological processes underlining this response. It is believed that active stresses depend on stretching and the concentration of free calcium ions in the cytoplasm of the smooth muscle cell. In turn, the calcium content depends on the membrane potential, determined by the pressure. An axisymmetric stationary problem is considered; the wall material in the non-activated state is assumed to be pseudoelastic. Calculations showed a qualitative difference in the dependence of active stress on stretching and its distribution in the radial direction before and after the development of the vascular response. The calculated diameter values before and after exposure to substances affecting the polarization of the smooth muscle cell membrane are within the range of experimental values. These results indicate that the introduction of the dependence of calcium concentration on membrane potential expands the area of applicability of simple models of this kind for evaluating the value of vascular diameter.

Functional preference and spatial response of urban renewal entities in Beijing

In the process of rapid urban renewal, quantitative research on functional preferences and spatial layout norms of multi-type urban renewal entities is crucial for optimizing spatial governance and promoting orderly control of urban renewal. We investigate urban renewal in Beijing from 2006 to 2021 using directional distribution, spatial autocorrelation, and hotspot analysis. The findings are as follows: (1) The functional preference of each type of entity differs. While most private companies and other profit-oriented entities concentrate on producer services and residential functions, policy-oriented entities dominate the urban regeneration of public service activities. (2) Every entity shows a significant agglomeration characteristic, yet exhibits a differentiated spatial response pattern. Those entities with stronger leasing ability prefer the central zone while others are the opposite. (3) Diverse types of entities have differentiated spatiotemporal evolutions. The spatial directional divergence of state-owned enterprises and scientific research institutes has increased between 2006 and 2021. This is mainly influenced by the policy of relieving Beijing of nonessential functions. However, the rest entities show a balanced spatial development trend with the difference in each direction becoming smaller. Furthermore, the center of gravity of profit-oriented entities has shifted from the suburbs to the central zone due to a combination of administrative and market forces, whereas the center of gravity of policy-oriented entities tends to move outward from the central zone.

Linear polarization study of open clusters in the anticenter direction: Signature of the spiral arms

Aims. Our objective is to investigate the distribution of dust and associated large-scale structures of the Galaxy using optical linear polarization measurements of various open clusters located at different distances in the Galactic anticenter direction. Methods. We present R-band linear polarization observations of stars toward five open clusters: Kronberger 1, Berkeley 69, Berkeley 71, Berkeley 19, and King 8 in the anticenter direction. The polarization observations were carried out using the ARIES (Aryabhatta Research Institute of Observational Sciences) IMaging POLarimeter mounted on the 104 cm Sampurnanand telescope of ARIES, Nainital, making it the first study to target the polarization observations toward distant clusters (~6 kpc). We combined the observed polarization data with the distance information from the Gaia space telescope to infer the dust distribution along the line of sight. Results. The variation in the degree of polarization and extinction with distance reveals multiple dust layers in each cluster direction. In addition, common foreground-dust layers detected toward different cluster directions highlight global features such as spiral arms. Our results show that the dust clouds at 2 kpc toward Berkeley 69 and Berkeley 71 coincide with the Perseus arm, while the dust layer at ~4 kpc toward the distant clusters Berkeley 19 and King 8 indicates the presence of the Outer arm. The large-scale dust distribution obtained by combining our polarization results with previous polarization studies of nearby open clusters suggests that the anticenter direction is characterized by a low-extinction homogeneous dust distribution with a somewhat uniform orientation of the plane-of-sky component of the magnetic field along the line of sight. Conclusions. Our study demonstrates that polarization is useful as a tool for studying the large-scale dust distribution and structural features where kinematic distance methods are inadequate and cannot provide accurate distances to the dust clouds. The global dust distribution in the anticenter direction shows signatures of the intervening spiral arms.

Analisis Strategi Pemasaran Dalam Meningkatkan Volume Penjualan Pada UD. Tahu Murni Kota Gunungsitoli

Marketing has a crucial role in increasing product sales and introducing products to consumers. UD. Tahu Murni, located in Gunungsitoli City, is a business that focuses on tofu production with additional tempeh products. Although the business is still in operation, tofu production shows stagnation, with an increase only occurring on weekends. This is due to the lack of effective marketing strategies to attract a wider consumer base. This study aims to evaluate the marketing strategies implemented by UD. Tahu Murni in an effort to increase its sales volume. The main focus of this research is to identify the constraints faced in the marketing strategy as well as to propose improvement measures. Based on the results of the study, it was found that the marketing strategy of UD. Tahu Murni has not been optimized. The business still relies on traditional marketing methods such as word of mouth, direct sales, and direct distribution, which have proven to be slow and inefficient in expanding the market. Improving product quality and product planning based on consumer complaints is not enough to significantly increase sales volume.

Detailed Insight into Gillnet Catches: Fish Directivity and Micro Distribution

Gillnets are widely used in research and commercial fishery activities. As passive gear, gillnets can be selective and dependent on the diel migration of fish. In areas with limited littoral extent, inshore–offshore migration may cause bias in the gillnet catch. Our hypothesis was that some factors, such as gillnet saturation, fish depletion, or chemical cues, could be the cause of the bias. We used a total of 66 CEN gillnets deployed at Římov Reservoir parallel to the shore at different positions of littoral-pelagic gradient. Individual fish direction was recorded from inshore, offshore, or unknown direction (i.e., entangled fish). A total of 5791 fishes from nine different species were caught. For most fish, it was possible to determine their directivity, and most fish were captured in littoral or first pelagic gillnets. Shallower and deeper benthic gillnets differed in their bleak (Alburnus alburnus) catch. No significant differences were found between fish directions. At the species level, only asp (Leuciscus aspius) and ruffe (Gymnocephalus cernua) showed differences between the captured directions in one case. The results support the assumption that gillnet capture is a random process that to a great extent is connected to random local movements. This is good news for fish monitoring projects. Sampling catch is likely to reflect true changes in the fish community, and not the effects of the deployment of the sampling gear. The experiment also showed that fish directivity statistics can be used for investigation of fish behavior and gear performance.

The Impact of Covid-19 Pandemic on Small Wineries in Cyprus and Reflections on Wine Tourism: Entrepreneurs’ Perspectives

Tourism-dependent countries like Cyprus, have been seriously affected by the shockwave that COVID-19 pandemic has generated to their sociocultural/economic fabric. One of the industries of Cyprus impacted is the wine industry. Indeed, the consequences of the pandemic have been reflected on various angles of the island’s wineries; from the day-to-day operations to their overall strategy. Moreover, they influenced their relationship to tourism and the provision of wine tourist experiences. This is even more apparent in the case of small wineries. In this respect, the paper examines how tourism related wine enterprises, and more specifically, small wineries in Cyprus, handled the crisis and its impacts, through the analysis of the wine entrepreneurs’ views. This study explores the dimensions of the pandemic imprinted on wineries’ business and highlights the pertinent measures taken to deal with them. Additionally, it illustrates how wine tourist activities have been affected, enhanced, and reformed for the smooth wine tourist experience to be provided. To do so, exploratory research was utilized to collect data through secondary sources and face-to-face in-depth interviews with winemakers/managers/owners of small wineries in Cyprus. Findings reveal that the greatest challenge that small wineries faced, was the high degree of uncertainty, as Hotels, Restaurants, and Catering companies (HO.RE.CA.) were temporarily closed and consequently, the wine consumption related to tourist flows was reduced. Small wineries took a series of measures to handle the crisis, such as emphasizing communications through online media, improving the provided -tourist- experience in the wineries, or enhancement of direct marketing and distribution strategies. The paper concludes with recommendations for small winemakers to deal with the shocks of crises and for their sustainable competitive advantage.

Spatially-varied crustal deformation indicating seismicity at faults intersection in the SE margin of the Tibetan Plateau: Evidence of S-wave splitting from microseismic identification

The Sanjiang Lateral Collision Zone (SLCZ) in the SE margin of the Tibetan Plateau is a special area where several strike-slip faults intersect, resulting in strong deformation and frequent earthquakes. We employ seismic waveforms recorded by a dense temporary broadband array (SJ array) and regional permanent stations to construct more complete microseismic catalogs by the microseismic identification in the SLCZ. New microseismic catalogs effectively increase the number of small earthquakes, revealing the details of the fault structures and providing many more records for S-wave splitting (SWS) analysis. It provides with an uncommon opportunity to detect the detailed upper crustal anisotropy in the fault intersection zone of SLCZ and to dissect the influence of faults, such as the Lijiang-Xiaojinhe fault and Red river fault, on crustal deformation. The spatial distribution of SWS parameters suggests multiple disturbance mechanisms to the upper crustal anisotropy in the study zone. Spatial distribution of dual dominant polarization directions of fast S waves near the block boundary faults uncovers the stress-focus range. Strong deformation from SWS data indicates frequent local seismicity. It reveals the spatial upper crustal deformation indicated by SWS parameters is closely related to not only stress, fault and local structure, but also local seismicity.

Spatial and Temporal Characteristics of Land Use Changes in the Yellow River Basin from 1990 to 2021 and Future Predictions

Studying spatial and temporal characteristics of land use changes and the driving factors in the Yellow River Basin as well as simulating and predicting future land use is crucial for resource management, ecological protection, and regional sustainable development in the Yellow River Basin. Based on the China Land Cover Dataset (CLCD) of the Yellow River Basin from 1990 to 2021, this study employs various methods such as the Mann–Kendall test and sliding t-test, land use dynamics, the land use transfer matrix, the standard deviation ellipse, the center of gravity migration model, and a geographic detector to explore the spatial and temporal characteristics of land use changes and driving forces in the Yellow River Basin over the past 30 years. Additionally, the study predicts land use types in the study area for the year of 2030 by using the Future Land Use Simulation (FLUS) model. The results show the following: (1) From 1990 to 2021, the area of forest, grassland, water, and impervious surfaces increased significantly, while the area of cropland, shrub, barren land, and wetlands decreased significantly. The most actively changing land use types are cropland, grassland, barren land, and impervious surfaces. (2) The center of gravity for shrub and impervious surfaces shifted westward, while wetlands showed a trend of obvious concentrated distribution, and the remaining land use types exhibited stable directional distributions. (3) Economic factors had a stronger driving effect on land use changes than topographic and climatic factors. The land use changes in the Yellow River Basin are influenced by the coordinated driving forces of multiple factors. (4) In 2030, the main land use types in the Yellow River Basin are still expected to be cropland, grassland, and forest. However, there will be a significant expansion of impervious surfaces and forest land, with substantial encroachment on cropland and grassland.

Pore-scale flame oscillations and patterns of upstream combustion wave propagation in a one-layer porous burner

Upstream propagation of filtration combustion wave in a one-layer porous burner is studied experimentally using thermal imaging and high-speed filming. The burner is the one-layer packed bed of spheres modeling porous media and providing optical access to the flame. This design allowed us to study macroscopic propagation of the combustion wave as well as non-stationary flame behavior at the pore scale. Experimental results demonstrate that upstream propagating combustion wave forms non-uniform porous medium temperature distribution in transverse direction which consists of hot areas separated by low-temperature regions. Macroscopic flame propagation can be accompanied by oscillations of some flame fragments at the pore scale. The mechanism of these pulsations is identical to the flames with repetitive extinction and ignition in narrow channels with external heating. Experimental results suggest that large scale evolution of the thermal wave affects the non-stationary behavior of the flame fragments at the pore scale and vice versa. The interplay between pore-scale and macro-scale processes manifests itself in the multiple repetitions of some patterns of the combustion wave propagation. Two most typical and common patterns are described and discussed. These patterns are step-wise transition of the flame fragment into the upstream pore and transition through the series of flame oscillations with repetitive extinction and ignition. It is shown that highly simplified one-dimensional model describes flame propagation in externally heated variable cross-section channel with heat conducting walls is capable to describe main features of these two patterns. Parametric study allows to predict the effect of problem parameters on the regions of existing of one or another pattern of upstream flame propagation.Novelty and Significance StatementThis paper presents new experimental data on temperature characteristics of upstream propagating filtration combustion wave in a one-layer porous burner. For the first time the patterns of combustion wave propagation uniting macro-scale processes of the thermal wave propagation and oscillations of the flame fragments at the pore scale are described on the basis of experimental data and numerical modeling. Results obtained for the one-layer burner can apparently be generalized to the case of combustion in three-dimensional porous media and packed beds. These results are significant because extend fundamental knowledge on porous media combustion by information on pore- and macro- scale flame dynamics as well as on the interplay of these scales. Experimental results can also be useful for validation of pore-resolved numerical simulations actively developed in the last decade.

Numerical Simulation Study on Rotary Air Preheater Considering the Influences of Steam Soot Blowing

The ash deposition is a general problem that needs to be solved effectively for the rotary air preheater of the coal-fired boiler. Taking the rotary air preheater of a 600 MW power station as the object, the mesh model of the flue gas side of the air preheater, considering the influences of steam soot blowing, is established using the Gambit 2.4.6 software. Based on the SIMPLE algorithm, the velocity field and the temperature field in the air preheater under varied working conditions are simulated using the software of Ansys Fluent 2021R1, and the influences of the boiler load, the operation parameters of the steam soot blower, and the running and outage of the soot blower on the flue gas velocity distribution in the depth direction of the corrugated plates, the soot-blowing coverage area, the inlet flue gas velocity, and the inlet flue gas temperature of the corrugated plates are analyzed. Under the base working condition, the flue gas velocity on the axis of the steam nozzle first decreases rapidly with increasing the corrugated plate depth (Z < 1.0 m), and then it decreases slowly with an almost equal slope. The longitudinal flue gas velocity has a positive correlation with the boiler load. The longitudinal flue gas velocity obviously decreases when the boiler load is decreased, and its reduction increases as the corrugated plate depth increases. It is one reason that the ash deposition is prone to occur on the cold end surface of corrugated plates under the condition of low boiler load. The longitudinal flue gas velocity increases with the soot-blowing steam velocity increasing when the corrugated plate depth is less than 1.5 m, but after that, it is almost not affected by the change in soot-blowing steam velocity. The soot-blowing coverage area has a negative correlation with the boiler load but a slight positive correlation with the steam velocity of the soot blower on the whole. The inlet flue gas velocity of the corrugated plates has a positive correlation with the boiler load and the inlet steam velocity of the soot blower. The average inlet flue gas velocity decreases by 21.7% when the boiler load is reduced by 50%. For every 5 m/s variation in the inlet steam velocity, the inlet flue gas velocity changes by about 10–14% whether the steam soot blower is put into operation or not, which has an obvious effect on the inlet gas velocity of the corrugated plates. The inlet flue gas temperature of the corrugated plates is, respectively, positively correlated with the boiler load and the inlet steam temperature of the soot blower. When the boiler load is reduced from 100% BMCR to 50% BMCR, the average inlet flue gas temperature of the corrugated plates is reduced by 44.2 K; however, when the soot-blowing steam temperature varies by 20 K, the average inlet flue gas temperature of the corrugated plates varies by only about 1.8 K. It means that it is difficult to enhance the cold end flue gas temperature of the corrugated plates only by raising the soot-blowing steam temperature at low boiler load. Adding a soot blower using high-temperature steam or hot air at the outlet of the corrugated plates may be an option to solve the ash deposition of the corrugated plates.

Multi-Fidelity Modelling of the Effect of Combustor Traverse on High-Pressure Turbine Temperatures

As turbine entry temperatures of modern jet engines continue to increase, additional thermal stresses are introduced onto the high-pressure turbine rotors, which are already burdened by substantial levels of centrifugal and gas loads. Usually, for modern turbofan engines, the temperature distribution upstream of the high-pressure stator is characterized by a series of high-temperature regions, determined by the circumferential arrangement of the combustor burners. The position of these high-temperature regions, both radially and circumferentially in relation to the high-pressure stator arrangement, can have a strong impact on their subsequent migration through the high-pressure stage. Therefore, for a given amount of thermal power entering the turbine, a significant reduction in maximum rotor temperatures can be achieved by adjusting the inlet temperature distribution. This paper is aimed at mitigating the maximum surface temperatures on a high-pressure turbine rotor from a modern commercial turbofan engine by conducting a parametric analysis and optimization of the inlet temperature field. The parameters considered for this study are the circumferential position of the high-temperature spots, and the overall bias of the temperature distribution in the radial direction. High-fidelity unsteady (phase-lag) and conjugate heat transfer simulations are performed to evaluate the effects of inlet clocking and radial bias on rotor metal temperatures. The optimized inlet distribution achieved a 100 K reduction in peak high-pressure rotor temperatures and 7.5% lower peak temperatures on the high-pressure stator vanes. Furthermore, the optimized temperature distribution is also characterized by a significantly more uniform heat load allocation on the stator vanes, when compared to the baseline one.

Laser Powder Bed Fusion of Multifunctional Bio-inspired Vertical Honeycomb Sandwich Structures: For the Application of Lightweight Bipolar Plates of Proton Exchange Membrane Fuel Cells

The bipolar plate (BPP) is a crucial component of proton exchange membrane fuel cells (PEMFC). However, the weight of BPPs can account for around 80% of a PEMFC stack, posing a hindrance to the commercialization of PEMFCs. Therefore, the lightweight design of BPPs should be considered as a priority. Honeycomb sandwich structures meet some requirements for bipolar plates, such as high mechanical strength and lightweight. Animals and plants in nature provide many excellent structures with characteristics such as low density and high energy absorption capacity. In this work, inspired by the microstructures of the Cybister elytra, a novel bio-inspired vertical honeycomb sandwich (BVHS) structure was designed and manufactured by laser powder bed fusion (LPBF) for the application of lightweight BPPs. Compared with the conventional vertical honeycomb sandwich (CVHS) structure formed by LPBF under the same process parameters setting, the introduction of fractal thin walls enabled self-supporting and thus improved LPBF formability. In addition, the BVHS structure exhibited superior energy absorption (EA) capability and bending properties. It is worth noting that, compared with the CVHS structure, the specific energy absorption (SEA) and specific bending strength of the BVHS structure increased by 56.99% and 46.91%, respectively. Finite element analysis (FEA) was employed to study stress distributions in structures during bending and analyze the influence mechanism of the fractal feature on the mechanical properties of BVHS structures. The electrical conductivity of structures were also studied in this work, the BVHS structures were slightly lower than the CVHS structure. FEA was also conducted to analyze the current flow direction and current density distribution of BVHS structures under a constant voltage, illustrating the influence mechanism of fractal angles on electrical conductivity properties. Finally, in order to solve the problem of trapped powder inside the enclosed unit cells, a droplet-shaped powder outlet was designed for LPBF-processed components. The number of powder outlets was optimized based on bending properties. Results of this work could provide guidelines for the design of lightweight BPPs with high mechanical strength and high electrical conductivity.