流量变现、价值创造与中国平台经济的高质量发展

平台经济是中国经济高质量发展的新空间、新引擎、新渠道和新支撑。随着平台用户增量触顶,中国平台经济整体上已经进入从增量竞争向存量竞争过渡的关键转型期,新发展阶段下实现平台经济的高质量发展要求对中国平台经济领域不同商业模式的核心特征、运行机制、外部性影响进行深入分析。首先,从降低市场交易成本、提升市场交易效率和平台与实体经济高质量融合三个方面论述平台经济高质量发展的核心内容;其次,分析流量变现和价值创造两种平台商业模式的主要特征及产生基础,并比较两种模式与平台经济高质量发展的一致性及其作用路径。研究表明,以用户真实需求为核心、以提升平台内交易效率为目的,最终能够实现多方互利的价值创造模式是中国平台经济高质量发展的内在要求。因此,政府应继续加强平台经济的科学监管,引导培育数字平台经济价值创造模式的外部基础,平台企业应该平衡流量变现模式和价值创造模式,加强数字技术的研发和推广应用。

Analysis of impact pressure,rock-breaking effect,and ground vibration induced by the disposable CO_(2)fracturing tube

The technology of expansion fracturing with liquid CO_(2)(EFLCO_(2))has attracted increasing attention due to reduced vibration and damage.The disposable fracturing tube has been developed and is gradually replacing the Cardox tube.However,there is a lack of impact pressure testing of disposable tubes under real working conditions,selection of gas explosion design parameters,and systematic analysis of blasting vibration.This limitation has constrained the widespread application of disposable fracturing tubes in engineering.A joint monitoring of the pressure-time curves in the disposable tubes and boreholes was conducted.The rock-breaking effect of varying hole spacing parameters in the EFLCO_(2)design was analyzed,and a systematic study was carried out on the vibration peak value,frequency,and energy characteristics.The results show that(1)the pressure distribution characteristics,stress peak value,and duration in the disposable tubes are different from those of Cardox tubes,which show multi-peak distribution,low-pressure peak value,and short duration.The correlation between the pressure in the disposable tube,filling pressure,and liquid CO_(2)weight is established,and a theoretical calculation method for the borehole wall pressure is proposed;(2)The hole spacing in rocks of different hardness is suggested;and(3)At the same scale distance,the peak particle velocity(PPV)caused by EFLCO_(2)(PPVCO_(2))is significantly smaller than that caused by blasting(PPVexplosive).The ratio of PPVexplosive to PPVCO_(2)is a power function related to scale distance,and a distance-related zonality exist in this relationship.The frequency composition of the vibration signal caused by EFLCO_(2)is relatively simple with a narrow frequency band.Its PPV and energy are mainly concentrated in the low-frequency band.This research contributes to the optimization of disposable fracturing tubes,gas explosion design,and vibration hazard control.

Observing eddy dye patches induced by shear instabilities in the surf zone on a plane beach

The effects of surf zone eddy generated by alongshore currents on the deformation and transport of dye are still poorly understood,and related tracer release experiments are lacking.Therefore,a tracer release laboratory experiment was conducted under monochromatic,unidirectional incident waves with a large incident angle(30°)on a plane beach with a 1:100 slope in a large wave basin.A charge-coupled device suspended above the basin recorded the dye patch image.The evolution of eddy dye patch was observed and the transport and diffusion were analyzed based on the collected images.Subsequently,a linear instability numerical model was adopted to calculate the perturbation velocity field at the initial stage.The observation and image processing results show that surf zone eddy patches occurred and were separated from the original dye patches.Our numerical analysis results demonstrate that the structure of the perturbation velocity field is consistent with the experimental observations,and that the ejection of eddy patches shoreward or offshore may be ascribed to the double vortex.

A case study of blasting vibration attenuation based on wave component characteristics

A typical blasting vibration wave is a composite wave,and its attenuation law is affected by the type of dominant wave component.The purpose of the present study is to establish an attenuation equation of the peak particle velocity(PPV),taking into account the attenuation characteristics of P-,S-and R-waves in the blasting vibration wave.Field blasting tests were carried out as a case to specifically apply the proposed equation.In view of the fact that the discrete properties of rock mass will inevitably cause the uncertainty of blasting vibration,we also carried out a probability analysis of PPV uncertainty,and introduced the concept of reliability to evaluate blasting vibration.The results showed that the established attenuation equation had a higher prediction accuracy,and can be considered as a promising equation implemented on more complex sites.The adopted uncertainty analysis method can comprehensively take account of the attenuation law of blasting vibration measured on site and discrete properties of rock masses.The obtained distribution of the PPV uncertainty factor can quantitatively evaluate the reliability of blasting vibration,which is a powerful and necessary supplement to the PPV attenuation equation.

春小麦品系‘MY002894’和‘YJ006793’成株期抗条锈病基因遗传分析

春小麦品系‘MY002894’和‘YJ006793’对小麦条锈病具有成株期抗性。本研究分析了这2个品系成株期抗条锈病基因遗传规律,促进其有效利用。通过‘MY002894’与‘Taichung 29’(T29)抗感杂交和‘MY002894’与‘YJ006793’抗抗杂交构建F 2∶3代分离群体,在青海省农林科学院植物保护研究所小麦条锈病自然病圃进行了两年的抗病表型鉴定。遗传分析结果显示,‘MY002894’与‘T29’F 2∶3杂交群体卡方测验符合7R∶9S的抗感分离比,表明‘MY002894’中含有2对独立作用的隐性成株期抗条锈病基因;‘MY002894’与‘YJ006793’F 2∶3群体卡方测验符合55R∶9S的抗感分离比,表明‘MY002894’与‘YJ006793’杂交F 2∶3杂交群体对条锈病的抗性由1对显性基因2对隐性基因独立控制。由于‘MY002894’中有2对独立作用的隐性成株期抗条锈病基因,推测‘YJ006793’中可能含有1对显性成株期抗条锈病基因。

Separation and enrichment of trace ractopamine in biological samples by uniformly-sized molecularly imprinted polymers

In order to prepare a high capacity packing material for solid-phase extraction with specific recognition ability of trace ractopamine in biological samples, uniformly-sized, molecularly imprinted polymers （MIPs） were prepared by a multi-step swelling and polymerization method using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker, and toluene as a porogen respectively. Scanning electron microscope and specific surface area were employed to identify the characteristics of MIPs. Ultraviolet spectroscopy, Fourier transform infrared spectroscopy, Scatchard analysis and kinetic study were performed to interpret the specific recognition ability and the binding process of MIPs. The results showed that, compared with other reports, MIPs synthetized in this study showed high adsorption capacity besides specific recognition ability. The adsorption capacity of MIPs was 0.063 mmol/g at 1 mmol/L ractopamine concentra- tion with the distribution coefficient 1.70. The resulting MIPs could be used as solid-phase extraction materials for separation and enrichment of trace ractopamine in biological samples.

A numerical model with Stokes drift for pollutant transport within the surf zone on a plane beach

This study examines the effects of Stokes drift on pollutant transport within the surf zone on a plane beach both numerically and experimentally. Firstly, the numerical model is described. The wave-induced current is modeled using the concept of the radiation stress. The wave propagation model is based on the wave energy conservation equation. And the advective diffusion model including the Stokes drift is used to describe the pollutant transport in the surf zone. Model validation was achieved in this case versus an analytical solution for an instantaneous point source in a uniform horizontal flow. This study also describes a laboratory experiment on dye release in the surf zone over a plane beach. We examined the final inclination angle required by a continuously released pollutant plume to reach the shoreline under both cases, and transport velocities in the alongshore and cross- shore directions were estimated by linearly fitting the location of a dye-patch front at different time. Results show that this dye patch moved shoreward with an approximate speed of 0.05 m/s (0.017 m/s) between 10 s and 40 s and 0.001 m/s (0.011 m/s) after 40 s for Case 1 (2). This model was then used to simulate pollutant transport in the surf zone on a plane beach as reproduced in the current experiment. Comparisons between our dye transport experiment and numerical results were then also conducted;the data showed that the numerical results including Stokes drift agreed more closely with experimental results than those without it. The data showed that the pollutant was generally transported obviously shoreward in addition to its expected drift along the shore. We also suggest that Stokes drift plays an important role in pollutant movement in the surf zone, especially shoreward.

纳米金对抗氧化剂的催化氧化及其活性的影响

目的:探讨纳米金对抗坏血酸和表儿茶素氧化进程的影响及其生物学效应。方法:合成5 nm左右的金纳米颗粒,通过紫外可见光谱研究金颗粒加入前后两种抗氧化剂的氧化速率,监测反应过程中氧气浓度的变化。采用电子自旋共振光谱研究作用前后抗氧化剂对不同种类自由基的清除能力。结果:加入纳米金后,抗坏血酸及表儿茶素的氧化速率迅速提高,此过程伴随氧气的大量消耗。同时,与纳米金作用后的抗氧化剂清除自由基的能力显著降低。结论:纳米金颗粒能催化氧化不同种类的抗氧化剂,并显著抑制其抗氧化功能。

Development of the electric automatic steering system for agricultural vehicles

Automatic guidance of agricultural vehicles requires automatic execution of operation commands received from the navigation controller by using electronically controlled mechanisms for wheel steering,speed changing and work implementing.Automatic steering contributes as a prerequisite technique in automatic and semi-automatic agricultural navigation.This research aimed to develop an electric automatic steering system that was compact in its structure and integrated into original steering mechanism in a simply and convenient way for aftermarket modification.A brushless motor and reducer assembly was utilized to provide an adequate steering torque instead of manual maneuver.A rapid assembling approach was proposed by passing the steering shaft through the hollow output shaft.A digital proportional-integral-differential(PID)algorithm was implemented to calculate the rotation speeds and directions by comparing the desired angle and the actual angle,which was implemented in a printed circuit board with a microcontroller unit(MCU)and interface chips.An unmanned wheeled tractor was applied as test platform to integrate the newly developed electric automatic steering system.Tests were conducted to evaluate its performance in terms of stability and responsiveness.An autonomous navigation system guided the tractor along target paths in the field by sending steering commands to the electric automatic steering system.The results show that the steering angle error was less than 0.81°when desired steering angle was less than 10°.The lateral error difference was no more than 4.76 cm when repeating following the same target path,which indicated that the electric automatic steering system responded accurately and robustly to steering commands.

Three new sesquiterpenes from roots of Curcuma longa

Objective:To study the chemical constituents from the roots of Curcuma longa.Methods:The structures of the compounds were elucidated based on extensive spectral analysis,including 1D and 2D NMR,MS,UV,and CD analysis.Results:Two new sesquiterpene compounds(1S,2R,5R,7S,8R)-2,8-epoxy-5-hydroxybisabola-3,10-dioen-9-one(1),(1R,2R,5R,7S,8R)-2,8-epoxy-5-hydroxybisabola-3,10-dioen-9-one(2),and a new natural product 6-(4-Hydroxymethylphenyl)-2-methyl-hept-2-ene-4-one(3)together with three known compounds ar-turmerone(4),2-methyl-6-(4-hydroxyphenyl-3-methyl)-2-hepten-4-one(5)and 2-methyl-6-(4-hydroxyphenyl)-2-hepten-4-one(6)were isolated from C.longa root extract with 95%ethanol.Conclusion:In the study,three new compounds were isolated from C.longa,and their absolute configurations were determined.

Clinical characteristics of hospitalized patients with 2019 novel coronavirus disease indicate potential proximal tubular dysfunction

In December 2019,highly infectious 2019 novel coronavirus disease(COVID-19)broke out in Wuhan,China.The pathogen was identified as 2019 novel coronavirus(2019-nCoV).[1]The 2019-nCoV had the capacity to cause systematic injury including renal injuries besides pneumonia.[2]Angiotensin-converting enzyme 2(ACE2)acts as a cell entry receptor for 2019-nCoV.[1]ACE2 expression was dominant in proximal tubules within the kidney.In this study,the clinical data from hospitalized patients were retrospectively analyzed at their admission to identify if there is any evidence of proximal tubule injury.

Angular momentum dependence of quasifission dynamics in the reaction ^(48)Ca+^(244)Pu

The quasifission dynamics in the reaction ^(48)Ca+^(244)Pu is investigated in the framework of time-dependent Hartree-Fock(TDHF)theory. The calculations are performed in three-dimensional Cartesian coordinate without any symmetry restrictions. The full Skyrme energy functional is incorporated in our TDHF implementation. The quasifission dynamics is quite sensitive to the angular momentum of colliding system. The contact time of quasifission decreases as a function of angular momentum and then forms a plateau with small oscillations. The quasifission process is accompanied by an important multi-nucleon transfer. The quantum shell effect plays a crucial role in the mass and charge of quasifission fragments. The mass-angle distribution of the fragments is calculated, which can be compared directly with future experiments.

Data mining and mathematical models in cancer prognosis and prediction

Cancer is a fetal and complex disease.Individual differences of the same cancer type or the same patient at different stages of cancer development may require distinct treatments.Pathological differences are reflected in tissues,cells and gene levels etc.The interactions between the cancer cells and nearby microenvironments can also influence the cancer progression and metastasis.It is a huge challenge to understand all of these mechanistically and quantitatively.Researchers applied pattern recognition algorithms such as machine learning or data mining to predict cancer types or classifications.With the rapidly growing and available computing powers,researchers begin to integrate huge data sets,multi-dimensional data types and information.The cells are controlled by the gene expressions determined by the promoter sequences and transcription regulators.For example,the changes in the gene expression through these underlying mechanisms can modify cell progressing in the cell-cycle.Such molecular activities can be governed by the gene regulations through the underlying gene regulatory networks,which are essential for cancer study when the information and gene regulations are clear and available.In this review,we briefly introduce several machine learning methods of cancer prediction and classification which include Artificial Neural Networks(ANNs),Decision Trees(DTs),Support Vector Machine(SVM)and naive Bayes.Then we describe a few typical models for building up gene regulatory networks such as Correlation,Regression and Bayes methods based on available data.These methods can help on cancer diagnosis such as susceptibility,recurrence,survival etc.At last,we summarize and compare the modeling methods to analyze the development and progression of cancer through gene regulatory networks.These models can provide possible physical strategies to analyze cancer progression in a systematic and quantitative way.

Preliminary Investigation of Preparing High Burn-Up Structure in Nuclear Fuel by Flash Sintering Using CeO_(2) as a Surrogate

The high burn-up structure(HBS)is characterized by the grain size of 100-300 nm and a porosity of up to 20%,which is formed at the rim of the nuclear fuel pellet due to 2-3 times higher local burn-up during the in-pile irradiation.HBS is considered a new potential structure for high-performance fuels.However,it is difficult to prepare HBS by conventional sintering methods.In this study,flash sintering was used to prepare HBS using CeO_(2)as a surrogate for a preliminary investigation.A new experimental configuration for rapid sintering of CeO_(2)pellets was provided,in which the green body can be rapidly preheated and pressure-assisted by the induction heating electrodes.An insulated quartz tube was used as the die for the flash sintered samples,allowing the current to flow through the sample and providing a stable condition for applying an external pressure of approximately 5.3-7.0 MPa during flash sintering process.Using an initial electric field of 141 V cm-1 and holding for 1-7 min at the maximum current density of~98 mA mm^(-2),CeO_(2)ceramics with a grain size of 114-282 nm and a relative density of 75.4-99.7%were prepared.The densification and microstructure evolution behaviors during flash sintering in this new experimental configuration have been discussed in detail.This new experimental configuration may provide a promising approach for preparing UO_(2)ceramics and their HBS.