DIRECT DISPLACEMENT OF PARALLEL MECHANISM WITH WAVELET NETWORK

A new method solution for the direct displacement of parallel mechanism, wavelet network method, is proposed. Comparing with the classical analytical and numerical methods, this method can be extended to any parallel mechanism with any selected degree of freedom and configuration. A wavelet network suiting to approach multi-input and multi-output system is constructed. The network is optimized by analyzing the sparseness of input data and selecting the fitting wavelets by orthogonalization method according to the output data. Then it is applied to solve the direct displace- ment of a general six-degree-of-freedom parallel mechanism as a numerical example. For comparison purposes, a BP neural network is also used for this problem. Simulation results show that the wavelet network performs better than BP neural network. In addition, the wavelet network learns much faster than BP network.

Effects of Key Agricultural Measures of Mechanized Direct Seeding Technology on Rapeseed Yield in Chengdu Plain

Mechanized direct sowing of rapeseed is a labor-saving and highly-efficient culture technique. In order to explore high-yield cultivation techniques suitable for Chengdu Plain, effects of several key agronomic measures＇, such as sowing date, density and N fertilizers, on development and yield formation were studied by strip and split plot experiment of three factors. The research showed that optimal condi- tions for direct seeding technology can be achieved provided with scientific sowing date, density and appropriate N fertilizers, and the research showed that rapeseed yield reached the peak at 320 g/m2, when sowing date was on September 3th, sow- ing density was 30 plant/m2, and nitrogen fertilizer was 27 g/m2.

（N-Z） Odd-Even Effect for the Non-Equilibrium Mechanism of （p, n） Reactions

The neutron spectra and angular distributions from （p,n） reactions in the input proton energy range 6-25 MeV were analyzed. These are the old experimental data, however, re-analysis of these data reveals very interesting peculiarities which never have been discussed before. The high energetic part of neutron spectrum due to the direct mechanism changes considerably from one isotope to other. This difference was described with incorporation of two components which provide the ＂broad bump＂, or ＂step like＂ shape of neutron spectra at high energy. The properties of these components are： different shape, energy shift between them, and very strong fluctuation between different isotopes for ratio of cross sections connected with partial contribution. One may conclude that shape of non-compound neutron spectrum demonstrates very strong （N-Z） odd-even effect. The direct comparison of experimental data, and semi-empirical results with （p,n） spectra predicted by the EMPIRE code, gave evidence that the traditional approach cannot predict this effect. New finding may explain the ＂constant temperature＂ dependence for level density in mass range A-60 discussed in several investigations. These new experimental peculiarities were demonstrated, and it may be considered as reality. At the same time there is not consequent physical model for their explanation. The fact that spectrum shape is correlated with N-Z value may give a hint that discussed effects are connected with ＂halo-neutrons＂.

Effects of different mechanical direct seeding methods on grain yield and lodging resistance of early indica rice in South China

Direct seeding of rice has become a main planting method due to the low labor input and high economic benefit in South China.Dry direct seeding(DDS)has been widely used for single-season rice planting establishment.However,few studies have examined the performance of early-season indica rice under mechanical dry direct seeding.A two-year field experiment was conducted with two indica rice cultivars(i.e.,Zhongjiazao 17 and Zhuliangyou 819)to study lodging characteristics and grain yield formation under DDS,flooded direct seeding(FDS)and wet direct seeding(WDS)patterns.The results showed that the annual grain yield in DDS was higher by 14.42–26.34%for cultivar ZLY819 and 6.64–24.58%for cultivar ZJZ17 than in WDS and FDS,respectively,and these increases were mainly attributed to the improvement of the panicles.The DDS pattern significantly increased the seedling emergence rate of early indica rice cultivars,and increased total dry weight and crop growth rate.Meanwhile,shorter basal internodes,better stem diameter and stem wall thickness and lower lodging index were found in DDS in contrast to FDS and WDS.In particular,DDS improved the stem lodging resistance.Our results suggested that the appropriate direct seeding method was beneficial for improving the grain yield and lodging resistance of early indica rice.

Bridging therapy and direct mechanical thrombectomy in the treatment of cardiogenic cerebral infarction with anterior circulation macrovascular occlusion

BACKGROUND Intravenous thrombolysis is an important treatment for cerebral infarction.However,it is difficult to achieve good results if the patient is complicated with anterior circulation macrovascular occlusion.In addition,the vascular recanalization rate is low,so mechanical thrombectomy,that is,bridging therapy,is needed AIM To investigate the efficacy and safety of bridging therapy and direct mechanical thrombectomy in the treatment of cardiogenic cerebral infarction with anterior circulation macrovascular occlusion.METHODS Ninety-six patients in our hospital with cardiogenic cerebral infarction with anterior circulation macrovascular occlusion from January 2017 to July 2020 were divided into a direct thrombectomy group(n=48)and a bridging group(n=48).Direct mechanical thrombectomy was performed in the direct thrombectomy group,and bridging therapy was used in the bridging treatment group.Comparisons were performed for the treatment data of the two groups(from admission to imaging examination,from admission to arterial puncture,from arterial puncture to vascular recanalization,and from admission to vascular recanalization),vascular recanalization rate,National Institutes of Health Stroke Scale(NIHSS)and Glasgow Coma Scale(GCS)scores before and after treatment,prognosis and incidence of adverse events.RESULTS In the direct thrombectomy group,the time from admission to imaging examination was 24.32±8.61 min,from admission to arterial puncture was 95.56±37.55 min,from arterial puncture to vascular recanalization was 54.29±21.38 min,and from admission to revascularization was 156.88±45.51 min,and the corresponding times in the bridging treatment group were 25.38±9.33 min,100.45±39.30 min,58.14±25.56 min,and 161.23±51.15 min;there were no significant differences between groups(P=0.564,0.535,0.426,and 0.661,respectively).There was no significant difference in the recanalization rate between the direct thrombectomy group(79.17%)and the bridging group(75.00%)(P=0.627).There were no significant differences between the direct thrombectomy group(16.69±4.91 and 12.12±2.07)and the bridging group(7.13±1.23) and(14.40±0.59)in preoperative NIHSS score and GCS score(P=0.200 and 0.203,respectively).After the operation,the NIHSS scores in both groups were lower than those before the operation,and the GCS scores were higher than those before the operation.There was no significant difference in NIHSS and GCS scores between the direct thrombectomy group(6.91±1.10 and 14.19±0.65)and the bridging group(7.13±1.23 and 14.40±0.59)(P=0.358 and 0.101,respectively).There was no significant difference in the proportion of patients who achieved a good prognosis between the direct thrombectomy group(52.08%)and the bridging group(50.008%)(P=0.838).There was no significant difference in the incidence of adverse events between the direct thrombectomy group(6.25%)and the bridging group(8.33%)(P=0.913).CONCLUSION Bridging therapy and direct mechanical thrombectomy can safely treat cardiogenic cerebral infarction with anterior circulation macrovascular occlusion,achieve good vascular recanalization effects and prognoses,and improve the neurological function of patients.

Directing Role of Cage Structure for Crystallization of Zeolites

The directing mechanisms of liquid directing agents of zeolite Y and zeolite L were studied by means of light transmission, ultracentrifugation, NMR, XRD and “cross-exchange” experiments. It was discovered that not only microcfystals of zeolites, but also cage structures of zeolites play the directing role for crystallization of zeolites.

Microstructure and mechanical properties of Ni3Al intermetallics prepared by directional solidification electromagnetic cold crucible technique

The present work focused on the Ni_3Al-based alloy with a high melting point. The aim of the research is to study the effect of withdrawal rate on the microstructures and mechanical properties of directionally solidified Ni-25 Al alloy. Ni_3 Al intermetallics were prepared at different withdrawal rates by directional solidification(DS) in an electromagnetic cold crucible directional solidification furnace. The DS samples contain Ni_3 Al and Ni Al phases. The primary dendritic spacing(λ) decreases with the increasing of withdrawal rate(V), and the volume fraction of Ni Al phase increases as the withdrawal rate increases. Results of tensile tests show that ductility of DS samples is enhanced with a decrease in the withdrawal rate.

Occurrence,Damage and Control Index of Rape Sclerotinia sclerotiorum in Mechanical Direct Seeding Fields

Real-time monitoring and investigation in fields showed that the disease starting period of Sclerotinia sclerotiorum in mechanical direct seeding fields was earlier. Disease conditions rose with the advancing growth stage, which grew more quickly during the early stage of anthesis, flower withering period and early si- lique mature period. Yield less rate increased with the increasing stem disease rate and disease index. Yield loss rate（ Y1 ） had extremely significant correlation with stem disease rate（X1 ）and disease index（X2 ）, and the related models were Y1 = 0. 544 330 2X1 -2. 316 1 （n = 14, r --0. 986 0 ＊ ＊ ）and YI = 0. 673 408 X2 - 1. 016 4 （ n = 14 ,r = 0.977 2 ~ ＊ ）, respectively. Disease control indexes for one time control against S. sclerotlorum in mechanical direct seeding fields were stem disease rate as 11.8% and disease index as 7.6, respectively. The control indexes for twice control against the disease were stem disease rate as 16.8% and disease index as 11.7. This paper provided a new scientific basis for preventing S. sclerotiorum in mechanical direct seeding fields.

Mechanism of Thaumasite Formation in Concrete

Significant efforts have been made in revealing the mechanism of thaumasite formation in concrete, which continues to be fraught with ambiguities and dissension. Chemical method was employed to synthesize pure C3S, C2S, C3A, ettringite, and thaumasite, and X-ray diffraction（XRD）, Raman spectroscopy and infrared spectroscopy（IR） were used to identify thaumasite from other hydrates. To investigate the direct route of thaumasite formation, C3S, C2S, gypsum, and calcium carbonate were used to prepare a cement paste so that the interference of ettringite formation can be avoided. The indirect route of thaumasite formation was also studied by considering the effect of C3A or ettringite content on thaumasite formation. Results show that thaumasite can be definitely generated in the absence of aluminium-bearing minerals or ettringite under appropriate conditions, while the ettringite presence promotes the thaumasite formation. No evidences support the heterogeneous nucleation route in this work. It is concluded that the method mentioned in this work can surely be used to investigate the mechanism of thaumasite formation, and thaumasite can form by both direct and woodfordite routes.

0D/3D direct Z-scheme heterojunctions hybridizing by MoS2 quantum dots and honeycomb conjugated triazine polymers (CTPs) for enhanced photocatalytic performance

Herein,a novel direct Z-scheme photocatalyst was accomplished by hybridization of 0D MoS2 quantum dots(MSQDs)and 3D honeycomb-like conjugated triazine polymers(CTP)(namely,CTP-MSQD).The unique 0D/3D hierarchical structure significantly enhanced the exposure of active sites and light harvesting property,while the formed p-n junction enabled the direct strong interface coupling without the necessity of any mediators.The optimized CTP-MSQD3 exhibited continuously increased visible-light-driven photocatalytic activity and strong durability both in Cr(VI)reduction and H2 evolution,featured a rate of 0.069 min^(-1) and 1070μmol/(hr•g),respectively,which were 8 times than those of pure 3D-CTP(0.009 min^(−1) and 129μmol/(hr•g)).We believe that this work provides a promising photocatalyst system that combines a 0D/3D hierarchical structure and a Z-scheme charge flow for efficient and stable photocatalytic conversion.

Gut Microbiota Brings a Novel Way to Illuminate Mechanisms of Natural Products in vivo

Poor bioavailability and undefined major/direct targets are two major obstacles for herbal medicines and natural products（NPs） to elucidate their precise mechanisms in vivo. Gut microbiota is an important bridge between eukayotic body and environment, which can interact with a majority of medicines with poor bioavailability and mediate their in vivo pharmacological activities. There are two main modes through which gut microbiota may mediate the pharmacological effects of NPs. First, gut microbiota catabolizes the NPs in herbal medicines into secondary metabolites with higher bioavialability and/or higher activity, facilitating the NPs enter circulation and exert beneficial impact at the pathological spot. Second, herbal medicines and NPs can favorably shift the compositional structure of gut microbiota, thereby performing remote functions to diseased organs/tissues via the systemic impaction of gut microbiota. In this review, the potential pathways were summarized through which gut microbes facilitate the pharmacological functions of herbal medicines and NPs and highlight the significance of gut microbiota in clarifying the in vivo mechanisms of herbal medicines and NPs.

Microstructure, Microsegregation, and Mechanical Properties of Directional Solidified Mg–3.0Nd–1.5Gd Alloy

The microstructure, microsegregation, and mechanical properties of directional solidified Mg–3.0Nd–1.5Gd ternary alloys were experimentally studied. Experimental results showed that the solidification microstructure was composed of dendrite primary a（Mg） phase and interdendritic a（Mg） · Mg12（Nd, Gd） eutectic and Mg5 Gd phase. The primary dendrite arm spacing k1 and secondary dendrite arm spacing k2 were found to be depended on the cooling rate R in the form k1= 8.0415 9 10-6R-0.279 and k2= 6.8883 9 10-6R-0.205, respectively, under the constant temperature gradient of40 K/mm and in the region of cooling rates from 0.4 to 4 K/s. The concentration profiles of Nd and Gd elements calculated by Scheil model were found to be deviated from the ones measured by EPMA to varying degrees, due to ignorance of the back diffusion of the solutes Nd and Gd within a（Mg） matrix. And microsegregation of Gd depended more on the growth rate, compared with Nd microsegregation. The directionally solidified experimental alloy exhibited higher strength than the non-directionally solidified alloy, and the tensile strength of the directionally solidified experimental alloy was improved,while the corresponding elongation decreased with the increase of growth rate.

Direct observation of dynamic surface reconstruction and active phases on honeycomb Ni_(3)N-Co_(3)N/CC for oxygen evolution reaction

Oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)are the key processes in water splitting.Compared with the two-electron process in HER,the four-electron process of OER is slow because of the more complex series of reactions.Therefore,a good understanding of the direct O_(2) evolution mechanism(DOEM)in OER is crucial to design high-efficiency catalysts to overcome the limitations imposed by the conventional adsorption evolution mechanism.In this work,honeycomb Ni_(3)N-Co_(3)N was prepared on carbon cloth(Ni_(3)N-Co_(3)N/CC)to investigate the DOEM.Density functional theory and in situ Raman scattering spectroscopy demonstrated that the OER process on Ni_(3)N-Co_(3)N/CC proceeded via the DOEM pathway,in which Ni_(3)N and Co_(3)N share the roles of dragging OH^(-),splitting off H-O bonds,and adsorbing other OH^(-),leading to significantly reduced Gibbs’s energy barriers of ΔG_(*OH) to ΔG_(O*)and ΔG_(O*)to ΔG_(O*OH).Moreover,the vertical honeycomb structure and conductive CC substrate contributed to the structural stability,conductivity,and quick O_(2) release capability.The Ni_(3)N-Co_(3)N/CC required low overpotentials of 320 and 495 mV to reach a current density of 10 and 100 mA cm^(-2),respectively.Moreover,the Ni_(3)N-Co_(3)N/CC delivered excellent stability with>90% retention of the initial current density over an 80-h-long test.

Review of precision rice hill-drop drilling technology and machine for paddy

Mechanized rice direct seeding is a cost-effective and efficient approach for rice cultivation.Recently,the use of rice direct seeding has been increasing rapidly owing to rural labour shortages and continuous increases in agricultural production costs.This article reviews the research and application progress of mechanized rice direct seeding including direct seeding technologies,precision rice seeding,precision rice seed-metering devices,key supporting agronomy technologies for mechanized rice direct seeding.South China Agricultural University developed precision rice hill-drop drilling(PRHDD)with synchronous furrowing and ridging technology and series machines for paddy that affords remarkable advantages in terms of saving time and labour,higher yield,and higher efficiency.In this approach,pre-germinated seeds are uniformly hill-dropped in the expected positions in puddled soil.It significantly improved the crop growth population and effectively solved the problems of high frequency of disease and pests caused by the irregular distribution of rice seeds with manual broadcasting,and generally reduces seed usage and increases the yield.Therefore,this technology has broad application prospects and great potential for promoting the development of mechanized rice direct seeding in China.

Control Parameter Optimization of Thermostatically Controlled Loads Using a Modified State-queuing Model

Thermostatically controlled loads(TCLs)are one of the best candidates to participate in direct load control(DLC).However,little attention is given to the parameter optimization of the TCLs control system due to the complexity of the TCLs’dynamics.In this paper,the parameters of the feedback control system based on the direct compressor control mechanism(DCCM)are optimized using the modified state-queuing(SQ)model,which can provide good characterizaton and greatly simplifies the dynamics of the TCLs.The simulation results verify the effectiveness of the proposed method.

One-to-Any Command and Control Model:Precisely Coordinated Operation on Uncooperative Controlled Nodes

New precisely cooperative attacks, such as the coordi- nated cross plane session termination （CXPST） attack, need thou- sands upon thousands machines to attack diverse selected links simultaneously with the given rate. However, almost all command and control（C＆C） mechanisms only provide publishing one com- mand to the whole once, so-called one-to-all C＆C model, and are not productive to support CXPST-alike attacks. In this paper, we present one-to-any C＆C model on coordination among the unco- operative controlled nodes. As an instance of one-to-any C＆C model, directional command publishing （DCP） mechanism lever- aging on Kademlia is provided with a range-mapping key creating algorithm for commands to compute the publishing range and a statistically stochastic node querying scheme to obtain the com- mands immediately. With theoretical analysis and simulation, it is indicated that one-to-any C＆C model fits for precisely coordi- nated operation on uncooperative controlled nodes with least complexity, better accuracy and efficiency. Furthermore, DCP mechanism can support one-to-all command publishing at the same time. As an example of future C＆C model, studying on one-to-any C＆C model may help to promote the development of more efficient countermeasures.