Radiation heat transfer model for complex superalloy turbine blade in directional solidification process based on finite element method

For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.

The Impact of Sun Radiation on the Thermal Comfort in Highly Glazed Buildings Equipped with Floor Heating Systems

Occupants of highly glazed buildings often suffer from thermal discomfort during the mid-seasons when no shadings are used in such buildings,especially when inertial heating systems are used.The present study is devoted to evaluating the impact of long solar beam exposure on the internal thermal discomfort in glazed spaces when heating is implemented through a floor system.A comprehensive experimental study is carried out using an experimental bi-climatic chamber which is fully monitored and controlled,allowing realistic simulations of the dynamic movement of the sun patch on a heated slab.The findings show that a period of discomfort as long as 8 h can occur,and persist far after the sunbeam exposure stops.During this period,the heating slab’s surface temperature,considered from an average point of view,can attain 34°C while the indoor temperature reaches 26°C.Simulations conducted using a previously developed model display a good fit with the measurements.

Analysis of solar radiation variations over Nanjing region in recent 40 years

The data utilized in this analysis consisted of extraterrestrial radiation, global radiation, d iffuse radiation, direct radiation, total cloud cover and relative suns hine. The annual variations and trend were analyzed for monthly mean daily total global, direct, and diffuse radiation on a horizontal surface and for the relations between global, direct, diffuse radiation and relative sunshine, tota l cloud cover. The climatological calculation equations of global and d irect radiation are put forward. The results show that global and dir ect radiations are characterized by decrease and diffuse radiation by increase. The main causes are due to the increase of concentration of suspended particles and atmospheric turbidities rather than cloud cover var iations.

Distributed modeling of direct solar radiation on rugged terrain of the Yellow River Basin

Due to the influences of local topographical factors and terrain inter-shielding, calculation of direct solar radiation （DSR） quantity of rugged terrain is very complex. Based on digital elevation model （DEM） data and meteorological observations, a distributed model for calculating DSR over rugged terrain is developed. This model gives an all-sided consideration on factors influencing th a resolution of 1 km × 1 km for thDSR. Using the developed model, normals of annual DSR quantity wie Yellow River Basin was generated, with DEM data as the general characterization of terrain. Characteristics of DSR quantity influenced by geographic and topographic factors over rugged terrain were analyzed thoroughly. Results suggest that： influenced by local topographic factors, i.e. azimuth, slope and so on, and annual DSR quantity over mountainous area has a clear spatial difference; annual DSR quantity of sunny slope （or southern slope） of mountains is obviously larger than that of shady slope （or northern slope）. The calculated DSR quantity of the Yellow River Basin is provided in the same way as other kinds of spatial information and can be employed as basic geographic data for relevant studies as well.

Radiation Absorption Mechanism in Nonvolatile MNOS Structure

The γ-ray radiation will speed up the discharge of the storedcharge in nonvolatile MNOS structure. The radiation absorptionmechanism to enhance the discharge is discussed. A direct radiationemission model from the interface traps distributing both in energylevel and in space is given. The theoretical results based on thismodel are in good agreement with experimental measurements.

Analysis of The Current Cituation of Solar Radiation Measurement

This paper mainly discusses the development status of solar radiation measurement technology,it expounds the relevant content of the current world radiation measurement datum and its standardization. Article the direct radiation from the sun,the main measuring principle of total radiation and scattering radiation,this paper discusses the different types of radiation survey measuring elements,measuring range,emphasis and the current widespread use of measurement instruments. The development trend of future solar radiation measurement is put forward,and it is emphasized that nanotechnology and spectrum technology will become the focus of solar radiation instrument research and development.

Multi-Band Antenna with Three Folded Monopoles for Mobile Communication Systems

This paper presents the design and the experimental characterization of a new multi-band antenna consisting of three folded monopoles dedicated to mobile communication systems. The originality of this paper is to get the PMR (Professional or Private Mobile Radio) band with the GSM (Global System for Mobile Communications), DCS (Digital Cellular System) and UMTS (Universal Mobile Telecommunications System) bands. The main lobe of the antenna radiates in the zenith direction with a linear polarization over all bands. It is interesting to design the proposed antenna in order to obtain better performances in terms of directive radiation pattern (especially in the PMR band) in comparison with the already existing antenna systems in the wireless market for similar purposes. The prototype was studied with the software CST-MWS (Micro wave studio 2012). The antenna has been designed and successfully measured.

Dosimetric evaluation of CR, 3DCRT and two types of IMRT for breast cancer after conservative surgery

Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-dimensional conformal radiation therapy (3DCRT), two-step intensity-modulated radiation therapy (TS-IMRT) and direct machine parameter optimization intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery. Methods: For each of 20 randomly chosen patients, 4 plans were designed using 4 irradiation techniques. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of the planning target volume received this dose. The cumulated DVHs and 3D dose distributions of CR, 3DCRT, TS-IMRT and DMPO-IMRT plans were compared. Results: For the homogeneity indices, no statistically significant difference was observed among CR, 3DCRT, TS-IMRT and DMPO-IMRT while the difference of the conformality indices were statistically significant. With regard to the organs at risk, IMRT and 3DCRT showed a significantly fewer exposure dose to the ipsilateral lung than CR in the high-dose area while in the low-dose area, IMRT demonstrated a significant increase of exposure dose to ipsilateral lung, heart and contralateral breast compared with 3DCRT and CR. In addition, the monitor units (MUs) for DMPO-IMRT were approximately 26% more than those of TS-IMRT and the segments of the former were approximately 24% less than those of the latter. Conclusion: Compared with CR, 3DCRT and IMRT improved the homogeneity and conformity of PTV, reduced the irradiated volume of OARs in high dose area but IMRT increased the irradiated volume of OARs in low dose area. DMPO-IMRT plan has fewer delivery time but more MUs than TS-IMRT.

Performance Assessment of Motorized Solar Photovoltaic Louvers System Using PVSYST Software

In the realm of technological market penetration of solar photovoltaic louvers(PVL)addressing environmental difficulties and the industrial revolution,a new avenue of renewable energy is introduced.Moreover,solar energy exploitation through building façades was addressed through motorized solar photovoltaic louvers(MPVL).On the other hand,proponents exalted the benefits of MPVL overlooking the typical analyses.In this communication,we attempted to perform a thorough industrial system evaluation of the MPVL.This communication presents a methodology to validate the industrial claims about MPVL devices and their economic efficiency and the insight on how geographical location influences their utilization and augment their potential benefits.This task is carried out by evaluating the extent of solar energy that can be harvested using solar photovoltaic system(PVSYST)software and investigating whether existing product claims are associated with MPVL are feasible in different locations.The performance and operational losses(temperature,internal network,power electronics)were evaluated.To design and assess the performance of different configurations based on the geographical analogy,simulation tools were successfully carried out based on different topographical locations.Based on these findings,various factors affect the employment of MPVL such as geographical and weather conditions,solar irradiation,and installation efficiency.tt is assumed that we successfully shed light and provided insights into the complexity associated with MPVL.

A bi-directional gap model for simulating the directional thermal radiance of row crops

Row crops are a kind of typical vegetation canopy between discrete canopy and continuous canopy.Kimes et al.studied the directional thermal radiation of row crops using the geometrical optical model,which simplified row structure as'box'and neglected the gap among foliage and did not consider the emissivity effects.In this work we take account of the gaps along illumination and viewing directions and propose a bi-direction gap model on the basis of the idea of gap probability of discrete vegetation canopy introduced by'Li-Strahler'and inter-correlation of continuous vegetation developed by Kuusk.It can be used to explain'hot spot'effects in thermal infrared region.The gap model has been validated by field experiment on winter wheat planted in shape of rows and results show that the gap model is better than Kimes'model in describing the directionality of thermal infrared emission for row crops.

A unified model of bidirectional reflectance distribution function for the vegetation canopy

An accurate and operational bidirectional reflectance distribution function （BDRF） canopy model is the basis of quantitative vegetation remote sensing. The canopy reflectance should be approximated as the sum of the single scattering reflectance arising from the sun, pl, and the multiple scattering reflectance arising from the canopy, fin, as their directional characteristics are dramatically different. Based on the existing BRDF model, we obtain a new analytical expression of ρ1 and ρm in this paper, which is suitable for different illumination conditions and different vegetation canopies. According to the geometrical optic model at the leaf scale, the anisotropy of ρ1 can be ascribed to the geometry of the object, sun and the sensor, multiple scale clumping, and the fraction of direct solar radiation and diffuse sky radiation. Then, we parameterize the area ratios of four components： the sunlit foliage, sunlit ground, shadow foliage and shadow ground based on a Poisson distribution, and develop a new approximate analytical single scattering reflectance model. Assuming G=0.5, a recollision probability theory based scattering model is developed which considers the effects of diffuse sky radiation, scattering inside the canopy and rebounds between the canopy and soil. Validation using ground measurements of maize and black spruce forest proves the reliability of the model.

PRELIMINARY NUMERICAL STUDY OF TOPOGRAPHIC EFFECTS OF THE TIBETAN PLATEAU ON SURFACE DIRECT RADIATION

To improve the simulating ability of a model,this paper presents a scheme of calculating direct radiation at land surface with topography in the model.A numerical study is conducted for the topographic effects of the Tibetan Plateau on the direct radiation using NCEP terrain data. Results show that,after taking account into the topographic radiation effect,the regional average of the radiation over the Plateau obviously increases in the local early morning and late afternoon, but changes less around noon.The effect is stronger in winter than that in summer.And heterogeneous topography has also affected the distribution of the radiation in this area.A simple numerical experiment shows that considering the effect will lead ground temperature to increase on the slope having more sunshine,and vice versa.

The influence of urban three-dimensional structure and building greenhouse effect on local radiation flux

Accurate measurements of the three-dimensional structure characteristics of urban buildings and their greenhouse effect are important for evaluating the impact of urbanization on the radiation energy budget and research on the urban heat island(UHI)effect.The decrease in evapotranspiration or the increase in sensible heat caused by urbanization is considered to be the main cause of the UHI effect,but little is known about the influence of the main factor“net radiant flux”of the urban surface heat balance.In this study,experimental observation and quantitative model simulation were used to find that with the increase of building surface area after urbanization,the direct solar radiation flux and net radiation flux on building surface areas changed significantly.In order to accurately quantify the relationship between the positive and negative effects,this study puts forward the equivalent calculation principle of“aggregation element”,which is composed of a building’s sunny face and its shadow face,and the algorithm of the contribution of the area to thermal effect.This research clarifies the greenhouse effect of a building with walls of glass windows.Research shows that when the difference between absorption rates of a concrete wall and grass is−0.21,the cooling effect is shown.In the case of concrete walls with glass windows,the difference between absorption rates of a building wall and grass is−0.11,which is also a cooling effect.The greenhouse effect value of a building with glass windows reduces the cooling effect value to 56%of the effect of a building with concrete walls.The simulation of changes in net radiant flux and flux density shows that the greenhouse effect of a 5-story building with windows yields 15.5%less cooling effect than one with concrete walls,and a 30-story building with windows reduces the cooling effect by 23.0%.The simulation results confirmed that the difference in the equivalent absorption rate of the aggregation element is the“director”of cooling and heating effects,and the area of the aggregation element is the“amplifier”of cooling and heating effects.At the same time,the simulation results prove the greenhouse effect of glass windows,which significantly reduces the cold effect of concrete wall buildings.The model reveals the real contribution of optimized urban design to mitigating UHI and building a comfortable environment where there is no atmospheric circulation.

Acoustic Radiation Analysis Based on Essential Solution of Green's Function

The principle objective of the paper is to study the acoustic radiation problem of the 3D space domain with control boundary. By using the conformal transformation theory, the Green's function for acoustic point source in the control domain space is obtained. With it, the expression of acoustic radiation function of the control domain is formed. Discussion about the acoustic radiation of pulsating sphere in right-angle space is drawn in the end, including the acoustic radiation directivity effect by the boundary characteristics, acoustic radiation frequency and acoustic source location. Numerical results show that: for the lower frequency radiation, the infection of free surface is significant; for the high frequency radiation, the infection of location is significant on the contrary. The research provides a new method for boundary characteristic problem of the structural-acoustic acoustic.

Observation and simulation of the diffuse attenuation coefficient of downwelling irradiance in the Polar Ocean

The three-stream radiation transfer model is used to investigate the fluctuation in the underwater diffuse attenuation coefficient of downwelling irradiance in the polar ocean with a high solar zenith angle and different direct radiation proportions.First,the applicability of the three-stream radiation model in the polar region is validated by using 18 in situ observation data from September to October 2009 in the Beaufort Sea.Statistics show that in the absence of sea ice,the average relative errors between the simulation and observation values for 490 nm downwelling irradiance (E_(d)(490)) and its diffuse attenuation coefficient (K_(d)(490)) are 7.04%and 9.88%,respectively.At the stations surrounded by sea ice,the radiation is relatively small due to ice blocking,and the average relative errors simulated by the model reach 15.89%and 15.55%,respectively.Second,simulations with different chlorophyll concentrations and different proportions of direct radiation reveal that a high solar zenith angle has a greater impact on K_(d)(490) in the surface water.K_(d)(490) is less affected by the light field (affected by the solar zenith angle and the proportion of direct radiation) at depths greater than 30 m,and meets the linear relationship with the inherent optical parameters(the sum of the absorption coefficient and backscattering coefficient).The surface K_(d)(490) is still consistent with that at a depth of more than 50 meters under a high solar zenith angle,implying that the surface K_(d)(490) can also be considered as an inherent optical parameter at a high solar zenith angle (greater than 60 degrees).The relative error of obtaining surface K_(d)(490) by using the linear relationship at the 50 m layer is found to be less than 8%in the seawater with chlorophyll concentration greater than0.05 mg m^(-3).The effect of the solar zenith angle and proportion of direct radiation can be ignored when measuring the diffuse attenuation coefficient in the polar region.Finally,the model can correct the ice-induced fluctuation in downward irradiance,allowing for optical research of seawater beneath the ice in the polar ocean.

Induced noise of impeller stuck and passive rotation state in multi-stage pump without power drive under natural flow conditions

The natural flow cooling strategy is commonly employed in modern high-speed vessels and nuclear-powered submarines. These vessels rely on the energy generated by their own speed to drive the cooling system and supply cooling water to the condenser. The circulating pump, which operates without a motor drive under natural flow conditions, is a large resistance component in the cooling system. However, it is also the primary noise source, significantly impacting the vessel’s safe operation and acoustic stealth performance. This study investigates the induced noise characteristics of a multi-stage pump under natural flow conditions by experiment, computational fluid dynamics (CFD), and acoustic finite element method. The analysis encompasses the distribution of the flow field, variations in acoustic power, spectral features of flow-induced noise, and directivity of external field radiation noise under different natural flow conditions. The results show that the acoustic power distribution is correlated with the flow field. When the impeller is stuck, the noise sources primarily concentrate in the flow separation area at the blade’s leading edge, the interface area between the impeller and the guide vane, and the flow shock area inside the guide vane. Conversely, when the impeller rotates passively, the blade wake area has a higher acoustic power. The flow noise spectrum under natural flow conditions mainly exhibits broadband and discrete characteristics. Additionally, the pump structure influences the external field radiation noise, and its directivity varies with different flow rates and characteristic frequencies. This study provides valuable insights into optimal design to reduce the noise of the circulating pump in the vessel’s natural flow cooling system. It is essential for ensuring the safe operation and acoustic stealth performance of high-speed vessels and nuclear-powered submarines.

Analysis of Atmospheric Turbidity in Clear Skies at Wuhan,Central China

The Angstr6m turbidity coefficient （β） and Linke turbidity factor （TL） are used to study the atmospheric conditions in Wuhan, Central China, using measureβd direct solar radiation during 2010-2011 in this study. The results show that annual mean β values generally increase from 0.28 in the morning to 0.35 at noon, and then decrease to 0.1 in the late afternoon during the day; annual mean TL generally varies from 3 to 7 in Central China. Both turbidity coefficients have maximum values in spring and summer, while minimum values are observed in winter months. It also reveals that β values show preponderance （52.8%） between 0.15 and 0.35, 78.1% of TL values are between 3.3 and 7.7, which can be compared with other sites around the world. Relationship between turbidity coefficients and main me- teorological parameters （humidity, temperature and wind direction） have been further investigated, it is discovered that the local aerosol concentrations, dust events in northern China and Southwest Monsoon from the Indian Ocean influences the β values in the study area.

Observation Study of Aerosol Radiative Properities over China

With a simplified radiation balance model, study is performed of aerosol direct radiation forcing in relation to its optical properties and surface reflectance, indicating that with the thickened aerosol layer the earth-atmosphere system may increase or weaken the solar radiation albedo, depending upon different combinations of aerosol single scattering albedo （SSA, ω^-o）, asymmetry factor （g）, and surface albedo （ag） rather than relying directly on the aerosol optical depth （δ）, which has its value just in proportion to the changed range of albedo alone. As indicated by the model results, systematic observations of aerosol radiative properties are required to make quantitative study of aerosol direct radiative forcing. Observational research of the properties has been undertaken based on ground and space measurements over China, including ground-based sunphotometeraerosol optical depth （AOD）, nephelometer-aerosol scattering coefficients, aethalometer-aerosol absorption coefficients, and MODIS products-retrieved AOD. The satellite retrieved AOD is validated against in situ sun photometer measured AOD, indicating that for eastern China remote sensing given AODs are acceptable owing mainly to lower surface reflectance there whereas for poor vegetation in the north of China the surface reflectance may be underestimated in AOD retrieval. However, appropriate modification of the scheme of aerosol remote sensing is likely to improve the retrieval accuracy. The aerosol single scattering albedo in dry condition is around 0.80 from surface-measured scattering and absorption coefficients. It requires further studies based on more observations to improve our understanding of the issue.

Direct wave and edge waves radiated into a solid medium by a circular thickness-mode transducer

The transient acoustic field radiated by a piezoelectric thickness-mode transducer into a solid medium is theoretically analysed. It is proved that the field consists of the direct wave, the longitudinal edge waves, the shear edge.waves, the head wave and the surface waves. The wavefront approximations of all these waves are given which result in a clear physical picture which is not only simple but also cotains the main features of the field. The theoretical result well describes the experiment.