Search

Ultrahigh-strength AerMet100 steel thick plate was fabricated by laser additive manufacturing process. The as-deposited microstructures of the test steel were characterized using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The mechanical properties were then examined using vickers-hardness test and tensile test. Results indicate that the as-deposited microstructures of the steel mainly consist of grain boundary allotriomorphic ferrite (GBA), grain interior irregular proeutectoid ferrite, plate-like upper bainite, needle-like lower bainite and retained austenite, which result in a good strength and some ductility anisotropy. The low deformation compatibility of specimen at the transverse direction (perpendicular to the deposition direction) mainly ascribes to the poor cracking resistance of the prior-austenite columnar grain boundary with coarse GBA phases. Compared to the almost intergranular cracking taken place in the transverse tensile specimen, the fracture mode of the longitudinal tensile specimen is a mixed mode of the predominant transgranular cracking and minor intergranular cracking.

The reactor fuel consumption calculation is an important part of reactor design and analysis, which usually needs to be completed iteratively by transport calculations and point-depletion calculations. AMAC is a newly versatile point-depletion and radioactive-decay code for use in simulation nuclear fuel cycles and calculating the nuclide compositions and radiation characteristics of materials. The code implements two depletion algorithms to treat the stiff depletion systems, including Transmutation trajectory analysis (TTA) method and Chebyshev rational approximation method (CRAM). With different higher-order approximations, the IPF form of CRAM is implemented to meet the high-precision requirements for the decay calculation of long-term nuclide system. And the accuracy analysis of higher-order CRAM is also discussed in the paper. In addition, the calculation of material radiation characteristics can be provided in AMAC to extend the application in different computational and analytical requirements. Then based on the complex nuclide system and a series of efficient programming methods, the high precision and efficiency of point-depletion calculation can be guaranteed. Three different calculation modes are supported by AMAC to execute the decay, constant flux and constant power calculations. By comparing with ORIGEN and FISPACT, the performance of AMAC in nuclide compositions and varieties of material radiation characteristics is proved and discussed. Furthermore, by coupling OpenMC and AMAC, the OECD/NEA burnup credit criticality benchmark and IAEA-ADS benchmark are used to validate the code performance of efficiency and precision in coupling calculations. All the results have shown good agreements with reference values and other codes, which demonstrates AMAC is a potential tool for accurate depletion calculation of reactors.

To give a deep insight into the nitrogen transfer mechanism during laser solid-state surface modification on titanium alloy, laser nitridation was conducted on Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy (TC11) without melting the metal surface. Microstructure characterizations of nitride layer formed under solid state condition were detailedly explored and the formation process of TiN phase was carefully discussed based on the lattice transformation. Results indicate that the nitride layer forming within a few seconds is composed of TiN phase layer and α phase layer with an orientation relationship: ( 1 1 ¯ 1 )TiN // (0001)α, [011]TiN // [ 2 11 ¯ 0 ]α. Formation of TiN phase experiences fast solid-state transformation from α phase. Phase transformation from α-Ti lattice to TiN lattice experiences orthorhombic lattice transformation due to the shear deformation caused by rapid interstitial solution of nitrogen. After repeated laser nitridation process upon three times, nitride layer was thickened with an improved hardness of 824 HV. Linearly reciprocating ball-on-plane wear tests indicate that wear resistance of laser nitridation samples could be enhanced by a factor of 13.

The high-energy input and thermal history during additive manufacturing lead to complex phase transformations in titanium aluminide alloy. This study mostly focuses on determining the solid-state phase transformation mechanisms during laser deposition and the failure mechanisms of alloys using molecular dynamics simulations. Because of the directional temperature gradient, columnar grains with fully lamellar microstructures are formed first after solidification. A narrow region just below the melting pool is reheated to high temperatures, thus enhancing the precipitation of new equiaxed grains. Multiple thermal cycles in the α + γ phase region promote the formation of massive γ phases (γm) at the grain boundaries. Finally, a nearly lamellar microstructure of alternating columnar and equiaxed grains with γm phases is formed. The deposited titanium aluminide alloy has good room and high-temperature (760 °C) tensile properties of 545 ± 9 and 471 ± 37 MPa, with elongations of 1.50 % ± 0.47 % and 1.50 % ± 0.45 %, respectively. The room and high-temperature samples both fail in the columnar grain region. The molecular dynamics simulations suggest that the interface between α2 and γm is the weakest, especially in the case of semicoherent interfaces (6° angle in the [1–10] direction), which provides good nucleation sites for cracks. Although the equiaxed grain regions contain several γm–α2 interfaces, the samples still fail in the columnar grain regions due to the increase in the cracking distance in the equiaxed regions caused by randomly oriented α2 + γ lamellae and the comparably good plasticity of the γm phases.

Taking the power load of an industrial park in Shanghai as an example in this paper, particle swarm optimization and cost-benefit model are employed to analyse the economy of new lithium-ion batteries, echelon lithium-ion batteries and lead-carbon batteries in photovoltaic energy storage systems in the whole life cycle. The research results showed that the economic order from large to small among different batteries in the photovoltaic energy storage system was new lithium-ion battery, echelon utilization lithium-ion battery and lead-carbon battery. The declines in energy storage cost and discount rate and the rise in peak electricity price can greatly improve the net present value of a photovoltaic-energy storage system (PV-BES) system.

Vortex electromagnetic (EM) waves with orbital angular momentum (OAM) offer a new degree of freedom for radar detection. Although to date few researches on target scattering characteristics of vortex EM waves have been reported. In this paper, the backscattering characteristics of vortex EM waves for a perfectly conducting wedge is investigated experimentally using the radar cross section (RCS) calibration measurement method. The experimental results show that for vortex EM waves, due to the specific spatial distribution, the RCS fluctuation of vortex EM waves is different from that of plane EM waves, and it varies with the OAM mode of the incident wave. The RCS of OAM beams is higher than that of the plane wave in some incident direction. This phenomenon indicates that vortex EM waves are more effective than plane EM waves to detect the low RCS target in some direction. And vortex EM waves of different OAM modes may be helpful to detect the low RCS target by increasing the RCS of the target.

Developing cheap and stable electrocatalysts is considered the key factor to achieve the large-scale application of fuel cells. In this paper, three-dimensional (3D) porous Co-doped vanadium nitride (VN) nanosheet-assembled microflowers are prepared with a facile solvothermal approach followed by nitridation at 500 °C in NH3. It is found that the microflower morphology and the Co doping both significantly enhance the oxygen reduction reaction (ORR) performance of the materials. Because the unique 3D porous structure provides higher specific surface area and more active sites as well as enriching the d electrons of V via doping, Co also improves the intrinsic activity of VN. Our optimal V0.95Co0.05N microflowers achieve a half-wave potential for the ORR of up to 0.80 V in 0.1 M KOH solution, which is almost comparable to that of commercial 20% Pt/C. More importantly, the catalysts show superior durability with little current decline (less than 12%) during chronoamperometric evaluation for over 25 000 s. Th...

Considering the complexity of data analysis caused by increasing urban load data, an Apache Spark based urban load analysis and forecasting technology is proposed in this paper. Firstly, the large-scale data processing platform is designed. Secondly, statistics of urban load data are processed by transformation and action in the form of resilient distributed datasets (RDDs). Thirdly, load forecasting model based on Dynamic Bayesian Network (DBN) is built for short-term urban load forecasting. GraphX is used for graph-parallel computation. Finally, the result of load analysis is presented and forecasting results of DBN are compared with other models. The comparison outcome shows that the DBN model implemented in Spark has better accuracy in load forecasting.

A study has been carried out in four rectangular section roadways with different supporting methods in Yuwu Coal Company (a longwall mine), by measurements of airflow velocities in cross-section of the roadways. The asymmetrical distributions of airflow in each roadway section was obtained. The paper analyzes the low airflow velocity region of roadways through the drawing of the distributions of airflow in each roadway section. The supporting methods influence the low airflow velocity region around the roof and wall of roadways. It is shown that the low airflow velocity region increase with surface roughness of the roof and wall. The high airflow velocity region was located around the floor of the roadway with rough roof and wall. However, in the roadways with smooth roof and wall the high airflow velocity region was located around the center of section. The risk assessment should be carried out in the low airflow velocity region in the roadway with rough roof and wall. To ensure the safety of coal mining, higher volume of air intake or more smooth roof and wall of the roadways should be achieved in a dangerous zone.

Fluoride salt cooled High temperature Reactor (FHR) attracts particular attention in the world because of its excellence in high power density and low operation pressure. However, it is difficult to simulate the discharge burnup of FHR at equilibrium state because of the changes of fuel element and fuel pebble position. At present, there are three methods used to estimate the attainable burnup of FHR: full core method, equilibrium bed method and infinite uniform bed method. These methods including refueling or searching equilibrium state consumes more computation time. Based on the infinite uniform bed method, this work introduces a new method to estimate the discharge burnup without needing to search equilibrium state. The obtained results from the new method are validated with those from the infinite uniform bed method in MOCUP and full core method in VSOP. It shows that the developed method can be used to estimate the discharge burnup in pebble-bed reactor.

A polarization and channel calibration technique used in dual polarization eight channel mono-pulse radar system is introduced in this paper. System error model is proposed. The method is based on equipments test and microwave chamber test without any calibrators. Cross-polarization error and amplitude-phase imbalances between different transmitting and receiving channels as well as different antenna sub-arrays can be extracted by using this method.

Laser melting deposition was carried out to deposit a 1Cr12Ni2WMoVNb steel bar on a wrought bar of same material. Room-temperature tensile properties of the hybrid fabricated 1Cr12Ni2WMoVNb steel sample were evaluated, and microstructure, fracture surface morphology, and hardness profile were analyzed by an optical microscope (OM), a scanning electron microscope (SEM), and a hardness tester. Results show that the hybrid fabricated 1Cr12Ni2WMoVNb steel sample consists of laser deposited zone, wrought substrate zone, and heat affected zone (HAZ) of the wrought substrate. The laser deposited zone has coarse columnar prior austenite grains and fine well-aligned dendritic structure, while the HAZ of the wrought substrate has equiaxed prior austenite grains which are notably finer than those in the wrought substrate zone. Besides, austenitic transformation mechanism of the HAZ of the wrought substrate is different from that of the laser deposited zone during the reheating period of the laser deposition, which determines the different prior austenite grain morphologies of the two zones. Microhardness values of both the laser deposited zone and the HAZ of the wrought substrate are higher than that of the wrought substrate zone. Tensile properties of the hybrid fabricated 1Cr12Ni2WMoVNb steel sample are comparable to those of the wrought bar, and fracture occurs in the wrought substrate zone during the tensile test.

Colloidal LiYbF 4 :Er 3+ nanorods were synthesized in an aqueous system which had the ratio of length to diameter of ∼2. These LiYbF 4 :Er 3+ nanorods emitted intense upconversion light under excitation of infrared at 1488 nm. Importantly, the intensities of two- and three-photon anti-Stokes upconversion PL bands were observed which were comparable to that of the Stokes emission under excitation with low power density. The plots of excitation power density versus emission intensity indicated that all the emissions centered at 549, 668, and 978 nm took a two-photon upconversion process. However, it could be simply deduced that the energy of two photons of 1488 nm were inadequate to produce a photon of 668 or 549 nm. For this conflict, the shape and saturation effects in the intermediate energy states were introduced to demonstrate the corresponding upconversion processes.

In our present study, we took advantage of the characteristics of RNA interference technology, which can efficiently, stably, and specifically silence target genes, and designed a small interfering RNA (siRNA) that could specifically target hTERT mRNA. We used a lentiviral vector (LV) to deliver the hTERT siRNA into telomerase-positive A549 lung cancer cells and investigated the effect of hTERT siRNA on the hTERT mRNA levels, hTERT protein levels, cell proliferation, and apoptosis in the lung cancer cells. The results from quantitative PCR, Western blotting, and the MTT assay showed that the expression levels of both hTERT mRNA and protein in the cells were significantly decreased and that the cell proliferation rate started to significantly slow down at 48 h after transfection with hTERT-LV. Our study demonstrated that siRNA sequences specifically targeting hTERT mRNA, which were packaged into lentivirus particles and then used to transfect the lung cancer cell line A549, can specifically silence the mRNA of the target gene, hTERT, and then reduce the hTERT protein expression level, which, in turn, reduces cell proliferation, inhibits cell growth, and induces apoptosis.

With the development of Internet, the amount of Information has been rapidly growing which is spread widely. In order to improve the value and accuracy of science information that is pushed in this paper, an intelligence dichotomous method for science information categorization to identify science information from massive Web news is presents. During the experiment, 85.3% recognition rate of the recognition non-tech news are realized and 82.9% accuracy rate, the results show that the method can effectively identify Web science information news and reduce the amount of independent news.

In order to improve the result of text dimension extraction, a text dimension reduction method which is based on CHI and TF-IDF is designed and realized. News websites on the Internet provide news articles, through the page analysis based on SVM and application method designed based on CHI and TF-IDF, good results achieved by extracting text dimensions from news website. According to the news articles from NetEase and ChinaNews, the proposed algorithm model of the text dimension extraction is designed and achieved 81.2% accuracy of the text classification, which provided the data support for the method designed. This method can make up a low frequency word defect of CHI and get efficient result on text classification.

In this work, a methodology for characterizing reservoir pore pressure and permeability during underbalanced drilling of horizontal wells was presented. The methodology utilizes a transient multiphase wellbore flow model that is extended with a transient well influx analytical model during underbalanced drilling of horizontal wells. The effects of the density behavior of drilling fluid and wellbore heat transfer are considered in our wellbore flow model. Based on Kneissl’s methodology, an improved method with a different testing procedure was used to estimate the reservoir pore pressure by introducing fluctuations in the bottom hole pressure. To acquire timely basic data for reservoir characterization, a dedicated fully automated control real-time data monitoring system was established. The methodology is applied to a realistic case, and the results indicate that the estimated reservoir pore pressure and permeability fit well to the truth values from well test after drilling. The results also show that the real-time data monitoring system is operational and can provide accurate and complete data set in real time for reservoir characterization. The methodology can handle reservoir characterization during underbalanced drilling of horizontal wells.

This paper presented the design of a side-feeding resistance-loaded antipodal Vivaldi antenna. The dimensions of the antenna have been simulated and analyzed with highfrequency electromagnetic simulation software HFSS. A sidefeeding antipodal Vivaldi antenna for 0.38~4.8GHz was designed and fabricated. And its impedance and radiation characteristics have been measured. The results show that the Vivaldi antenna can match well within the 0.38-4.8GHz and has a good radiating directivity. Compared with traditional Vivaldi antenna, a side-feeding and resistance-loaded antipodal antenna can reduce the antenna's size effectively on the one hand and an increase of the parasitic patch can improve antenna's gain on the other hand. Keywords-antipodal Vivaldi antenna;side-feeding;resistanceloaded

It was mainly analysed a S-band printed quadrifilar helical antenna for communication devices in this paper. And a dielectric loaded wide beam printed quadrifilar helical antenna was designed. A two-stage isolation resistor was placed in wilkinson power divider. The simulation results of this antenna agree well with the measured results.According to the simulation results and measured results,the antenna had a good heart-shaped radiation pattern from 3.05GHz to 3.45GHz, 3dB power-width was more than 160°,the gain was greater than -2dB in the azimuth range, the axial ratio was lower than 5dB, and the VSWR was lower than 1.4. this printed quadrifilar helical antenna had good electromechanical characteristics,and low cost.

A salience network (SN), mainly composed of the anterior insula (AI) and anterior cingulate cortex (ACC), has been suggested to play an important role in salience attribution which has been proposed as central to the pathology of paranoid schizophrenia. The role of this SN in the pathophysiology of paranoid schizophrenia, however, still remains unclear. In the present study, voxel-based morphometry and resting-state functional connectivity analyses were combined to identify morphological and functional abnormalities in the proposed SN in the early-stage of paranoid schizophrenia (ESPS). Voxel-based morphometry and resting-state functional connectivity analyses were applied to 90 ESPS patients and 90 age- and sex-matched healthy controls (HC). Correlation analyses were performed to examine the relationships between various clinical variables and both gray matter morphology and functional connectivity within the SN in ESPS. Compared to the HC group, the ESPS group showed significantly reduced gray matter volume (GMV) in both bilateral AI and ACC. Moreover, significantly reduced functional connectivity within the SN sub-networks was identified in the ESPS group. These convergent morphological and functional deficits in SN were significantly associated with hallucinations. Additionally, illness duration correlated with reduced GMV in the left AI in ESPS. In conclusion, these findings provide convergent evidence for the morphological and functional abnormalities of the SN in ESPS. Moreover, the association of illness duration with the reduced GMV in the left AI suggests that the SN and the AI, in particular, may manifest progressive morphological changes that are especially important in the emergence of ESPS.

We present in this paper a wave coupling theory of linear electro-optic (EO) effect for quasi-phase matched (QPM) of focused Gaussian beam in an optical superlattice (OSL). The numerical results indicate that, due to the EO effect of an appropriate applied electric field, the output beam will form spatially inhomogeneous polarization, changing continuously in transverse section of beam; the confocal parameter has a significant impact on the output polarization of Gaussian beam and determines the half-wave voltage.

The flow shop scheduling problem is a branch of production scheduling, which is among the hardest combinatorial optimization problem, and represents an important area in production scheduling. In this paper, a new effective hybrid algorithm is proposed which is based on plant growth simulation algorithm for permutation flow shop scheduling with the criterion to minimize the maximum completion time (makespan). In the algorithm, a directed graph which is based on the characteristic of flow shop scheduling problem representation is developed, and an efficient exchangeable node set is proposed and incorporated into plant growth simulation algorithm. Simulation results based on well-known benchmarks and comparisons with standard genetic algorithm demonstrate the effectiveness of the proposed bionic algorithm.

Atrial natriuretic peptide (ANP) is a vasodilator peptide primarily produced in the heart. Locally synthesized ANP has been found in reproductive tissues of various mammals and humans, and plays an important role in rat oocyte maturation and human sperm function. The objective of the present study was to determine the effects of ANP on the function (acrosome reaction and zona penetration) of giant panda spermatozoa. In fresh and frozen-thawed spermatozoa that had been preincubated for 2.5h, treatment with ANP (for 60 min) significantly increased the proportion of acrosome-reacted spermatozoa; maximal response (an acrosome reaction in 18.3 and 21.8% of fresh and frozen-thawed spermatozoa, respectively) was detected at 1 nM ANP. Treatment with C-ANP-(4-23), an analogue of ANP and specific binder to natriuretic peptide receptors-C (NPRC), had no significant effect on the acrosome reaction. However, the cyclic guanosine 5'-monophosphate (cGMP)-dependent protein kinase (PKG) inhibitor KT5823 completely abolished the effect of ANP on acrosome reaction. The effects of ANP, caffeine and heparin on frozen-thawed sperm function were studied by insemination of porcine salt-stored oocytes in a modified Tris-buffered medium (mTBM). The presence of ANP, caffeine or heparin in the insemination medium resulted in a higher proportion (P < 0.05) of oocytes with spermatozoa in the zona and perivitelline space (PVS), and a higher average number of spermatozoa/oocyte (P < 0.05) in the zona and PVS. However, in the absence of ANP, caffeine and heparin, there were no oocytes with a spermatozoon in the PVS. There were no differences among ANP, caffeine or heparin treatments for the proportion of oocytes penetrated or average number of spermatozoa/oocyte in the zona and PVS. In conclusion, we inferred that ANP induced the acrosome reaction of preincubated giant panda spermatozoa by a PKG pathway. Furthermore, ANP enhanced the penetrability of porcine salt-stored oocytes by frozen-thawed giant panda spermatozoa.

We propose theoretically a method for designing a narrowband multi-wavelength Solc-type filter based on the linear electro-optic effect in aperiodically poled lithium niobate. As one of its applications we demonstrate a thermally tuned 100 GHz spaced four-wavelength filter, whose working electric field is only 0.219 kV mm − 1 in an 8 cm long crystal. The filter allows four wavelengths to pass simultaneously with a 3 dB bandwidth of 0.26 nm, a passband of 32.5 GHz and a channel isolation of more than 8 dB, which can be tuned by temperature in a wide range at a rate of − 0.69 nm °C − 1. It is found that the domain errors of the aperiodically poled lithium niobate crystal within 25% are beneficial to the performance of the filter. The filter will be useful for dense wavelength division multiplexing optical communication systems.

We theoretically investigate the electro-optic coupling in an optical superlattice of linear chirped-periodically poled lithium niobate. It is found that the electro-optic coupling in such optical superlattice can work in a wide wavelength range. Some of examples, with bandwidths of 20, 40, 80, 120 nm, are demonstrated. The way to determine the electric field for perfect conversion between o- and e-ray and the method using apodized crystals of tanh profile to reduce the ripples are shown. As one of its applications, one kind of broadband Solc-type bandpass filter in optical communication range is proposed.