Research on conversion time between lost circulation and overflow for the fractured stratum

A new model was established based on the flow model of the drilling fluid in one-dimensional radial fracture to research the influencing factors on conversion time between lost circulation and overflow for multi-pressure system in fractured reservoirs.And the equation of the conversion time between lost circulation and overflow is obtained by solving the mathematical model.The model were validated by reproducing the field data from Sichuan oil field and the simulation results of references.The influences of consistency index,liquidity index,dynamic shear force,drilling fluid density,drilling fluid intrusion depth,pressure of lost circulation layer,crack width,decreased height of annular liquid level,pressure of high-pressure layer were analyzed.Results indicate that conversion time between lost circulation and overflow increases with the increasing consistency index,liquidity index,dynamic shear force,drilling fluid density,drilling fluid intrusion depth,pressure of lost circulation layer.Conversion time between lost circulation and overflow decreases with the increasing crack width,decreased height of annular liquid level,pressure of high-pressure layer.The time interval of“Hang's Muddingoff”operating should be appropriately less than the conversion time between lost circulation and overflow.Under the premise of ensuring wellbore safety,appropriately increasing the consistency index,liquidity index and dynamic shear force of the drilling fluid can effectively increase the conversion time between lost circulation and overflow in large fractured stratum.

Time-aware conversion prediction

The importance of product recommendation has been well recognized as a central task in business intelligence for e-commerce websites. Interestingly, what has been less aware of is the fact that different products take different time periods for conversion. The ＂conversion＂ here refers to actu- ally a more general set of pre-defined actions, including for example purchases or registrations in recommendation and advertising systems. The mismatch between the product＇s ac- tual conversion period and the application＇s target conversion period has been the subtle culprit compromising many exist- ing recommendation algorithms. The challenging question： what products should be recom- mended for a given time period to maximize conversion--is what has motivated us in this paper to propose a rank-based time-aware conversion prediction model （rTCP）, which con- siders both recommendation relevance and conversion time. We adopt lifetime models in survival analysis to model the conversion time and personalize the temporal prediction by incorporating context information such as user preference. A novel mixture lifetime model is proposed to further accom- modate the complexity of conversion intervals. Experimental results on two real-world data sets illustrate the high good- ness of fit of our proposed model rTCP and demonstrate its effectiveness in time-aware conversion rate prediction for ad- vertising and product recommendation.

High-precision time and frequency measurement method combining time-space conversion and different frequency phase detection

According to the time&space conversion relations and different frequency phase detection principle,an ultra-high precision time&frequency measurement method is proposed in this paper.The higher accuracy and stability of the speed of light and electromagnetic signals during the transmission in space or a specific medium enable the measurement of short time interval which uses the coincidence detection of signal’s transmission delay in length.The measurement precision better than 10 picoseconds can be easily obtained.The method develops the length vernier utilizing the stability of signal’s transmission delay,minimizes the fuzzy region of phase coincidence between the standard frequency signal and the measured signal,approaches the best phase coincidences and therefore improves the measurement precision which is higher than the precision provided by the traditional methods based on frequency processing.Besides,the method costs less than the traditional methods and can also solve the problem of the measurement of super-high frequency.Experimental results show the method can improve the measurement precision to 10 12/s in the time&frequency domain.

Modification of CaO-based sorbents prepared from calcium acetate for CO_2 capture at high temperature

CaO-based sorbent is considered to be a promising candidate for capturing CO_2 at high temperature. However,the adsorption capacity of CaO decreases sharply with the increase of the carbonation/calcination cycles. In this study, CaO was derived from calcium acetate(CaAc_2), which was doped with different elements(Mg, Al,Ce, Zr and La) to improve the cyclic stability. The carbonation conversion and cyclic stability of sorbents were tested by thermogravimetric analyzer(TGA). The sorbents were characterized by N_2 isothermal adsorption measurements, scanning electron microscopy(SEM) and X-ray diffraction(XRD). The results showed that the cyclic stabilities of all modified sorbents were improved by doping elements, while the carbonation conversions of sorbents in the 1st cycle were not increased by doping different elements. After 22 cycles, the cyclic stabilities of CaO–Al, CaO–Ce and CaO–La were above 96.2%. After 110 cycles, the cyclic stability of CaO–Al was still as high as 87.1%. Furthermore, the carbonation conversion was closely related to the critical time and specific surface area.

煤低温氧化动力学参数测试方法对比研究

针对现有研究缺乏对不同煤低温氧化动力学参数测试方法的对比分析,采用Coats-Redfern法、q/m法及Starink等转化率法3种测试方法分别计算煤低温氧化动力学参数,并以煤氧化自热反应时间和自燃临界堆积厚度作为对比参量比较3种方法的准确性。通过绝热氧化装置和同步热分析仪进行了煤样在纯氧和贫氧条件下的绝热氧化实验、多升温速率实验和恒温实验。根据热分析实验结果,分别采用3种方法计算煤低温氧化动力学参数。依据获得的动力学参数计算煤氧化自热反应时间和自燃临界堆积厚度。将计算结果与实测的煤氧化自热反应时间和采空区实际遗煤厚度进行对比,评价3种方法的准确性。实验结果表明:①通过绝热氧化实验实测的煤氧化自热温度变化率随时间的推移均逐渐增大;采用Coats-Redfern法计算得到的温度在0~8 h(q/m法为0~10 h)内几乎不发生变化,超过这一时间段后温度迅速升高;采用Starink等转化率法获得的温度变化趋势与绝热氧化实验实测结果类似。②采空区实际遗煤厚度大于Coats-Redfern法计算得到的临界堆积厚度;采用q/m法获得的临界堆积厚度超过了该工作面所在煤层厚度,与实际明显不符;采用Starink等转化率法获得的计算结果与实际较为接近。③采用Starink等转化率法获得的预测结果与实测结果更为接近,表明Starink等转化率法得到的煤低温氧化动力学参数较其他2种测试方法更为准确。

Effect of light conversion agent on luminous properties of a new down-converting material SrAl_2O_4:Eu^(2+),Dy^(3+)/light conversion agent

A new luminous material SrAl2O4：Eu^2＋,Dy^3＋/light conversion agent that can emit red light in the darkness after being excited was fabricated by combining light conversion agent on to SrAl2O4：Eu^2＋,Dy^3＋ particles through YsiX3.The morphology of the luminous materials was analyzed by scan electron microscopy（SEM）.The emission behavior was evaluated by fluorescence spectrophotometric analysis and the results demonstrated that the emission spectra of samples had a redshift compared to SrAl2O4：Eu^2＋,Dy^3＋ and the emission intensity rose dramatically at first and then decreased when the ratio of light conversion agent doping was over 1.4 wt.%.And the emission color of SrAl2O4：Eu^2＋,Dy^3＋/light conversion agent was tuned from green（SrAl2O4：Eu^2＋,Dy^3＋）to orange-red.Furthermore,the afterglow property was also investigated,and the results indicated that the afterglow brightness reached 6.5 cd/m^2,and as the light conversion agent concentration increased the brightness intensity decreased.

A unified framework of temporal information expression in geosciences knowledge system

Time is an essential reference system for recording objects,events,and processes in the field of geosciences.There are currently various time references,such as solar calendar,geological time,and regional calendar,to represent the knowledge in different domains and regions,which subsequently entails a time conversion process required to interpret temporal information under different time references.However,the current time conversion method is limited by the application scope of existing time ontologies(e.g.,“Jurassic”is a period in geological ontology,but a point value in calendar ontology)and the reliance on experience in conversion processes.These issues restrict accurate and efficient calculation of temporal information across different time references.To address these issues,this paper proposes a Unified Time Framework(UTF)in the geosciences knowledge system.According to a systematic time element parsing from massive time references,the proposed UTF designs an independent time root node to get rid of irrelevant nodes when accessing different time types and to adapt to the time expression of different geoscience disciplines.Furthermore,this UTF carries out several designs:to ensure the accuracy of time expressions by designing quantitative relationship definitions;to enable time calculations across different time elements by designing unified time nodes and structures,and to link to the required external ontologies by designing adequate interfaces.By comparing the time conversion methods,the experiment proves the UTF greatly supports accurate and efficient calculation of temporal information across different time references in SPARQL queries.Moreover,it shows a higher and more stable performance of temporal information queries than the time conversion method.With the advent of the Big Data era in the geosciences,the UTF can be used more widely to discover new geosciences knowledge across different time references.

Early therapeutic interventions of traditional Chinese medicine in COVID-19 patients:A retrospective cohort study

Objective:To observe the early interventions of traditional Chinese Medicine(TCM)on the conversion time of nucleic acid in patients with coronavirus disease 2019(COVID-19),and find possible underlying mechanisms of action.Methods:A retrospective cohort study was conducted on 300 confirmed COVID-19 patients who were treated with TCM,at a designated hospital in China.The patients were categorized into three groups:TCM1,TCM2 and TCM3,who respectively received TCM interventions within 7,8–14,and greater than15 days of hospitalization.Different indicators such as the conversion time of pharyngeal swab nucleic acid,the conversion time of fecal nucleic acid,length of hospital stay,and inflammatory markers(leukocyte count,and lymphocyte count and percentage)were analyzed to observe the impact of early TCM interventions on these groups.Results:The median conversion times of pharyngeal swab nucleic acid in the three groups were 5.5,7 and16 d(P<0.001),with TCM1 and TCM2 being statistically different from TCM3(P<0.01).TCM1(P<0.05)and TCM3(P<0.01)were statistically different from TCM2.The median conversion times of fecal nucleic acid in the three groups were 7,9 and 17 d(P<0.001).Conversion times of fecal nucleic acid in TCM1 were statistically different from TCM3 and TCM2(P<0.01).The median lengths of hospital stay in the three groups were 13,16 and 21 d(P<0.001).TCM1 and TCM2 were statistically different from TCM3(P<0.01);TCM1 and TCM3 were statistically different from TCM2(P<0.01).Both leucocyte and lymphocyte counts increased gradually with an increase in the length of hospital stay in TCM1 group patients,with a statistically significant difference observed at each time point in the group(P<0.001).Statistically significant differences in lymphocyte count and percentage in TCM2(P<0.001),and in leucocyte count(P=0.043)and lymphocyte count(P=0.038)in TCM3 were observed.The comparison among the three groups showed a statistically significant difference in lymphocyte percentage on the third day of admission(P=0.044).Conclusion:In this study,it was observed that in COVID-19 patients treated with a combination of Chinese and Western medicines,TCM intervention earlier in the hospital stay correlated with faster conversion time of pharyngeal swab and fecal nucleic acid,as well as shorter length of hospital stay,thus helping promote faster recovery of the patient.The underlying mechanism of action may be related to improving inflammation in patients with COVID-19.