Oil oxidation in the whole temperature regions during oil reservoir air injection and development methods

The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into four different parts: dissolving and inflation region, low temperature oxidation region, medium temperature oxidation region and high temperature oxidation region. The reaction mechanisms of different regions were explained. Based on the oil oxidation characteristics and filed tests results, light oil reservoirs air injection development methods were divided into two types: oxygen-reducing air flooding and air flooding;heavy oil reservoirs air injection in-situ combustion development methods were divided into two types: medium temperature in-situ combustion and high temperature in-situ combustion. When the reservoir temperature is lower than 120 ℃, oxygen-reducing air flooding should be used for light oil reservoir development. When the reservoir temperature is higher than 120 ℃, air flooding method should be used for light oil reservoir development. For a normal heavy oil reservoir, when the combustion front temperature is lower than 400 ℃, the development method is medium temperature in-situ combustion. For a heavy oil reservoir with high oil resin and asphalting contents, when the combustion front temperature is higher than 450 ℃, the development method at this condition is high temperature in-situ combustion. Ten years field tests of air injection carried out by PetroChina proved that air has advantages in technical, economical and gas source aspects compared with other gas agents for oilfield gas injection development. Air injection development can be used in low/super-low permeability light oil reservoirs, medium and high permeability light oil reservoirs and heavy oil reservoirs. Air is a very promising gas flooding agent.

STUDY ON AUSTENITE-FERRITE TRANSFORMATION WITHIN CRITICAL TEMPERATURE REGION

his paper deals with the phase trans formation of austenite to ferrite within the critical temperature region(between Ac1 and Ac3).The results show that the volume fraction of trans formation of ferrite formed isothermally from austenite is mainly varied with the austenitizing temperature.The higher the austenitizing temperature,the more volume fraction of the ferrite formed isothermally from austenite.Besides,the phase trans formation of austenite to ferrite within the critical temperature region was checked by austenitizing isothermal time.The volume fraction of ferrite formed isothermally from austenite within the critical temperature region for different isothermal time has heen examined experimen tally.The lglg(l-fv)-1 vs lgt relation does not follow the Avrami equation strictly and consists of two straight lines.

Identifying Regional Prolonged Low Temperature Events in China

This study examined regional prolonged low temperature （PLT） events in China from the observational station data for the period 1960–2008 using the new criteria. The new definition of a site PLT event is that the daily minimum temperature does not exceed the 10th percentile threshold of the local daily minimum temperature climatology for at least 5 days at a station. The regional PLT event is defined as at least five adjacent stations exhibiting site PLT simultaneously for 5 d. Under the new definition, 552 regional PLT events were identified, and three indices： duration, extent, and intensity, as well as a comprehensive index （CI） were used to quantify the event severity. In addition, geographical patterns and temporal variations of regional PLT events were investigated using three event categories： strong, moderate, and weak. Spatially, strong events were mainly located in the north of Xinjiang and along the Yangtze River to the south of the Yangtze River; moderate events occurred in Xinjiang and south of the Yangtze River; and weak events occurred south of the Yellow River. The variation for the annual frequency of regional PLT events in China in the last 49 years showed a significant decreasing trend with a rate of-1.99 times per decade, and the significant transition decade was the 1980s.

Treatable focal region modulated by double excitation signal superimposition to realize platform temperature distribution during transcranial brain tumor therapy with high-intensity focused ultrasound

Recently, the phase compensation technique has allowed the ultrasound to propagate through the skull and focus into the brain. However, the temperature evolution during treatment is hard to control to achieve effective treatment and avoid over-high temperature. Proposed in this paper is a method to modulate the temperature distribution in the focal region. It superimposes two signals which focus on two preset different targets with a certain distance. Then the temperature distribution is modulated by changing triggering time delay and amplitudes of the two signals. The simulation model is established based on an 82-element transducer and computed tomography （CT） data of a volunteer＇s head. A finite- difference time-domain （FDTD） method is used to calculate the temperature distributions. The results show that when the distances between the two targets respectively are 7.5-12.5 mm on the acoustic axis and 2.0-3.0 mm in the direction perpendicular to the acoustic axis, a focal region with a uniform temperature distribution （64-65 ℃） can be created. Moreover, the volume of the focal region formed by one irradiation can be adjusted （26.8-266.7 mm3） along with the uniform temperature distribution. This method may ensure the safety and efficacy of HIFU brain tumor therapy.

Spatiotemporal distribution characteristics and attribution of extreme regional low temperature event

Based on an objective identification technique for regional low temperature event（OITRLTE）, the daily minimum temperature in China has been detected from 1960 to 2013. During this period, there were 60 regional extreme low temperature events（ERLTEs）, which are included in the 690 regional low temperature events（RLTEs）. The 60 ERLTEs are analyzed in this paper. The results show that in the last 50 years, the intensity of the ERLTEs has become weak; the number of lasted days has decreased; and, the affected area has become small. However, that situation has changed in this century.In terms of spatial distribution, the high intensity regions are mainly in Northern China while the high frequency regions concentrate in Central and Eastern China. According to the affected area of each event, the 60 ERLTEs are classified into six types. The atmospheric circulation background fields which correspond to these types are also analyzed. The results show that, influenced by stronger blocking highs of Ural and Lake Baikal, as well as stronger southward polar vortex and East Asia major trough at 500-h Pa geopotential height, cold air from high latitudes is guided to move southward and abnormal northerly winds at 850 h Pa makes the cold air blow into China along diverse paths, thereby forming different types of regional extreme low temperatures in winter.

The effect of living environment on developmental disorders in cold regions

Developmental disorders(DDs)are a kind of chronic maladies,which can cause serious irreversible detriment to children’s physical and mental health.It is predominantly regulated by the interaction of environment and heredity.Cold regions are mainly located in the high latitudes of China.Their living environment is characterized by frequent cold wave,huge temperature difference,severe air pollution,high calorie diet,less exercise,smoking,drinking,etc.In recent years,substantial advances have been made in studies of the correlation between the living environment features in cold regions and the DDs.Accordingly,this article reviews the impact of the peculiar living environment of cold regions on DDs,with a view to provide fresh prevention strategies for reducing the morbidity of DDs in China cold regions by ameliorating living environment.

Spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River during the period 2002–2011 based on the Advanced Microwave Scanning Radiometer for the Earth Observing System(AMSR-E) data

Detecting near-surface soil freeze-thaw cycles in high-altitude cold regions is important for understanding the Earth＇s surface system, but such studies are rare. In this study, we detected the spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River（SRYR） during the period 2002–2011 based on data from the Advanced Microwave Scanning Radiometer for the Earth Observing System（AMSR-E）. Moreover, the trends of onset dates and durations of the soil freeze-thaw cycles under different stages were also analyzed. Results showed that the thresholds of daytime and nighttime brightness temperatures of the freeze-thaw algorithm for the SRYR were 257.59 and 261.28 K, respectively. At the spatial scale, the daily frozen surface（DFS） area and the daily surface freeze-thaw cycle surface（DFTS） area decreased by 0.08% and 0.25%, respectively, and the daily thawed surface（DTS） area increased by 0.36%. At the temporal scale, the dates of the onset of thawing and complete thawing advanced by 3.10（±1.4） and 2.46（±1.4） days, respectively; and the dates of the onset of freezing and complete freezing were delayed by 0.9（±1.4） and 1.6（±1.1） days, respectively. The duration of thawing increased by 0.72（±0.21） day/a and the duration of freezing decreased by 0.52（±0.26） day/a. In conclusion, increases in the annual minimum temperature and winter air temperature are the main factors for the advanced thawing and delayed freezing and for the increase in the duration of thawing and the decrease in the duration of freezing in the SRYR.

Diffusion welding process and joint's microstructure behavior of SiC_w/6061Al composite

The rules such as process parameters affecting joint properties and theevolution principle of weld's microstructure have been researched by adopting diffusion weldingprocess to connect SiC_w/6061Al composite. Experimental results show that there exists a criticaltemperature region between solid and liquid phase line of SiC_w/6061Al composite, and the regionwill shrink with the increasing of welding pressure. When diffusion welding occurred under thecritical temperature region, welding joint exhibits bad property of bonding, and the matrix and thereinforcement can't bond effectively. When diffusion welding occurred in the critical temperatureregion, the strength of welding joint changes widely with the variation of welding temperature. Whenwelding temperature varies in 10 deg C, the strength of welding joint will change obviously. Onlywhen welding temperature is higher than the critical temperature region, stable joint properties canbe obtained. Simultaneously the matrix and the reinforcement has better interfacial bonded indiffusion welding interface, and no obvious interface reaction occurred, and thus diffusion weldingof SiC_w/6061 Al composite can be successfully realized.

Temperature characteristics research of SOI pressure sensor based on asymmetric base region transistor

Based on the asymmetric base region transistor, a pressure sensor with temperature compensation circuit is proposed in this paper. The pressure sensitive structure of the proposed sensor is constructed by a C-type silicon cup and a Wheatstone bridge with four piezoresistors（R_1, R_2, R_3 and R_4/locating on the edge of a square silicon membrane. The chip was designed and fabricated on a silicon on insulator（SOI） wafer by micro electromechanical system（MEMS） technology and bipolar transistor process. When the supply voltage is 5.0 V, the corresponding temperature coefficient of the sensitivity（TCS） for the sensor before and after temperature compensation are -1862 and -1067 ppm/℃, respectively. Through varying the ratio of the base region resistances r_1 and r_2, the TCS for the sensor with the compensation circuit is -127 ppm/℃. It is possible to use this compensation circuit to improve the temperature characteristics of the pressure sensor.

GaN-based violet laser diodes grown on free-standing GaN substrate

A violet laser diode （LD） structure is grown on a free-standing c-plane GaN substrate and 4 μm×800μm ridge waveguide LDs are fabricated. The electrical and the optical characteristics of LDs under different facet-coating and chip-mounting conditions are investigated under pulse mode operation. The active region temperatures of p-side up and p-side down mounted LDs are calculated with different injection currents. The calculated thermal resistances of p-side up and p-side down mounted LDs are 4.6 K/W and 3 K/W, respectively. The threshold current of the p-side down mounted LD is much lower than that of the p-side up mounted LD. The blue shift of the emission wavelength with increasing injection current is observed only for the LD with p-side down mounting configuration, due to the more efficient heat dissipation.

Determining hydrothermal deactivation mechanisms on Cu/SAPO-34 NH_(3)-SCR catalysts at low-and high-reaction regions:establishing roles of different reaction sites

Hydrothermal deactivation is a constant chal-lenge in commercial catalytic process aimed at NOx emission control,which may be observed in the low(150-400℃)or high(400-550℃)-reaction regions.To the best of our knowledge,there is a lack of systematic research regarding the correlation between the reaction sites and the mechanism of hydrothermal degradation at various reaction regions.For a targeted investigation of this,Cu/zeolite catalysts have been prepared using different amounts of polyvinyl alcohol for adjusting their redox and acid properties.These catalysts exhibit hydrothermal deactivation in different reaction regions.No change is observed in the reaction mechanism even with hydrother-mal deactivation,but various reaction sites determine the performance deterioration in the low-and high-reaction regions.The redox properties and weak acid sites affect the hydrothermal deactivation in the low-reaction region,whereas the moderate/strong acid sites related to the structure mainly influence the hydrothermal deactivation in the high-reaction region.This work provides several the-oretical insights for optimizing the hydrothermal stabilities of Cu/zeolite catalysts.

1961-2018年北极冬季气温升高对黑龙江冷冬的影响及机制

With the advent of climate change,winter temperatures have been steadily increasing in the middle-to-high latitudes of the world.However,we have not found a corresponding decrease in the number of extremely cold winters.This paper,based on Climatic Research Unit(CRU)re-analysis data,and methods of trend analysis,mutation analysis,correlation analysis,reports on the effects of Arctic warming on winter temperatures in Heilongjiang Province,Northeast China.The results show that:(1)during the period 1961-2018,winter temperatures in the Arctic increased considerably,that is,3.5 times those of the Equator,which has led to an increasing temperature gradient between the Arctic and the Equator.An abrupt change in winter temperatures in the Arctic was observed in 2000.(2)Due to the global warming,an extremely significant warming occurred in Heilongjiang in winter,in particular,after the Arctic mutation in 2000,although there were two warm winters,more cold winters were observed and the interannual variability of winter temperature also increased.(3)Affected by the warming trend in the Arctic,the Siberian High has intensified,and both the Arctic Vortex and the Eurasian Zonal Circulation Index has weakened.This explains the decrease in winter temperatures in Heilongjiang,and why cold winters still dominate.Moreover,the increase in temperature difference between the Arctic and the Equator is another reason for the decrease in winter temperatures in Heilongjiang.