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poly (p-phenylene terephthalamide) (PPTA) fiber, a new strategic material, has excellent mechanical properties, chemical corrosion resistance and flame retardant properties, and is widely used in aerospace, national defense, civil and other fields. The mechanical properties, relative molecular weight, aggregate structure and fiber surface and internal defects of four samples of para-aramid fibers were studied, and the relationship between properties, structure and defects of fibers was established. The results show that the relative molecular weight of PPTA is one of the important factors affecting the mechanical property of the fibers with the same chemical molecular structure, and the tensile strength and modulus of fibers increase with the increase of the relative molecular weight. The tensile strength of para-aramid is mainly related to its crystallinity, orientation, surface defects and internal microporous defects, among which crystallinity and micro-defects are two important factors. The fiber modulus is mainly related to its orientation, and the influence of crystallinity and fiber internal and external defects on fiber modulus is relatively small. [ABSTRACT FROM AUTHOR]

In the work practice,the different countries,different standard involute spline will be often encountered,such as the Chinese National Standard（ GB Standard）,the International Organization for Standardization（ ISO） standard,the Deutsch Industrial Norman（ DIN） standard,the American National Standards Institute（ ASNI） standard,the Japanese Industrial Standards（ JIS）,French standard（ NF） and the like. There are modular system,pitch system,dual pitch system,the pressure angle has 30°,37. 5°,45°,etc.,the definition method of accuracy class is different. The common used involute splines are introduced and contrasted,and the relationships between the different standards are analyzed,a reference for industrial application is provided.

Major factors that cause damage in drilling in unconsolidated sandstone heavy oil reservoirs include: invasion of solids in drilling fluid, incompatibility between the liquid phase of drilling fluid and crude oil, and hydration and expansion of reservoir clay minerals. Therefore, a solid-free weak gel drilling fluid system for horizontal wells to protect the formations was developed that contains seawater + 0.1%–0.2% NaOH + 0.2% Na2CO3+ 0.7% VIS + 2.0% FLO + 2.0% JLX, weighed with KCl or sodium formate. The drilling fluid system has unique rheological properties, temporally independent gel strength, and excellent lubricating and inhibition performance. It is compatible with formation fluids, it not only meets the needs of horizontal well drilling, but also effectively protects the reservoir. The technique is well performed in tens of horizontal wells in offshore oilfields, such as WC13-1, BZ34-1, NP35-2, and BZ25-1 oilfields. 摘要: 钻井过程中造成疏松砂岩稠油油藏发生损害的主要因素是：钻井液固相侵入、钻井液液相与原油不配伍及储集层黏土矿物水化膨胀。为此研制出适于疏松砂岩稠油油藏储集层保护的无固相弱凝胶水平井钻井液体系：海水+0.1%～0.2%NaOH+0.2%Na2CO3+0.7%VIS+2.0%FLO +2.0%JLX，用KCl或甲酸盐加重。该钻井液具有独特的流变性能，凝胶强度无时间依赖性，具有优异的润滑性能和抑制性，与储集层流体配伍性好，不仅能够满足水平井钻井作业需要，而且具有优异的储集层保护效果，经文昌13-1油田、渤中34-1油田、南堡35-2油田、渤中25-1油田等数十口海上油田水平井验证，效果良好。 Key words: unconsolidated sandstone, heavy oil reservoir, formation damage, horizontal well, solid-free weak gel drilling fluid

A heavy medium cyclone was used to pre-throw a low-grade scheelite with high calcium carbonate from Hunan, in which the grade of WO3 is 0.31%, CaF2 is 9.23% and CaCO3 is 39.36%. The results of - 15 + 0.5 mm full size and fraction size pretreatment test show that there is little difference between full size pretreatment and fractional size pretreatment. Under the condition of 2.37 g/cm³ heavy medium pretreatment, the light product yield is 46.24%, WO3 recovery is 5.15%, CaF2 recovery is 27.17% and CaCO3 recovery is 74.72%. Using BK418 as collector of scheelite, the effects of heavy medium pre-throwing on scheelite flotation at room temperature were investigated. Results of flotation tests show that the tungsten concentrate containing 6.54% WO3 at ambient temperature is obtained after heavy medium pre-throwing, which is 3.77 percentage points higher than that before pre-throwing. The recovery of WO3 is 81.45%, which is 2.61 percentage points higher than that before pre-throwing. The heavy medium pre-throwing greatly reduces the grinding amount, improves the flotation index, saves the storage capacity of the tailings reservoir, and simultaneously the pre-thrown light product can be used as a building material raw material, thereby increasing the added value of the tailings. [ABSTRACT FROM AUTHOR]

Drilled wells reveal that the drilling fluid for Lower Fars salt-gypsum bed in Middle East has such problems as poor Theological property, lost circulation and overflow, etc. A composite saturated brine fluid with a density of 2.30 g/cm³ was developed, whose PV is 53 mPa·s, YP is 15 Pa and API filtration loss is less than 2 mL; its HTHP filtration loss is 8 mL under 120 ℃/3.5 MPa; its filter cake thickness is 1 mm; the recovery rates of salt-gypsum sample and mudstone sample are 88% and 79% respectively. When contaminated by 10% NaCl, 1% CaCl2 and 8% bad soil, its rheological property changed little, with filtration was less than 3.5 mL, lubricity was less than 0.1, fracture width was 200m, and the cumulative loss under 5 MPa was 2.4 mL/3 min. It can not only meet the drilling of Lower Fars salt-gypsum bed in the Middle East, but also provide experiences for drilling of salt-gypsum bed in similar oilfield in other countries. [ABSTRACT FROM AUTHOR]

For deeply buried and high formation fracturing pressure of deep water ultra deep reservoir, it is difficult to break the rock stratum and the pressure-bearing requirements for fracturing equipment and pipe strings are extremely high. So fracturing operation in deep water reservoir always faces high construction pressure and high risk, meanwhile, the limited space makes it difficult to equip large fracturing equipment on offshore platforms or operating support vessels. In order to minimize the construction scale, reduce wellhead injection pressure, this paper discussed an autogenetic heat and high temperature resistant high-density fracturing fluid system, and then performance evaluation in the laboratory and in-situ friction measurement were conducted for this new fracturing fluid system. The experiment results show that the density of fracturing fluid was 1.5 g/cm³, and friction reducing rate can reach to 59.6% with temperature resistant of 140 °C.Introduction of autogenetic-heat system has greatly shortened the breaking time of fluid and the associated gas could promote fracturing fluid flowback after gel breaking. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to screen high-performance ammonia oxidizing bacteria ( AOB) resistant to a high concentration of ammonia-nitrogen and low C/N ratio, for the development of novel AOB agents., Methods: Multi-point sampling, compulsory domestication, gradient dilution of domestication liquid were conducted to screen AOB with efficient and stable ammonia-nitrogen removing ability, and effects of different factors on its ammoxidation ability including C/N ratio, shaking speed and ammonia-nitrogen concentration were studied. Dominant strains were screened and identified by morphological observation, physiological and biochemical properties test and 16S rRNA sequence analysis., Results: Three efficient AOB were obtained, among them a micro-flora named JQ8 showed the highest activity. The ammonia-nitrogen removal rate reached 95. 07% in a simulated wastewater with 17. 86 mmol/L of initial ammonia-nitrogen at C/N 4 treated by JQ8 for 6 days. Moreover, its ammonia nitrogen removal rate kept above 95% and net nitrogen removing rate nearly 80% in the solution with a C/N ratio above 4 and an NH₄⁺-N concentration below 28.57 mmol/L. The circuit board industry wastewater was treated using the laboratory-simulated aerobic active sludge disposal system. The removal rate of NH₄⁺-N and total nitrogen reached 87.8% and 67.6% respectively after 7 days' treatment using JQ8. Defluvibacter sp., Paracoccus sp. and Aquamicrobium sp. were identified as the dominant strains after the composition analysis of JQ8., Conclusion: An ammonia oxidizing bacteria consortium JQ8 screened from the landfill leachate showed a strong ammonium-nitrogen removal and endurance ability under low C/N ratio and high ammonia-nitrogen concentration, thus is probably applicable to intensify the ammonia-nitrogen removal treatment of industrial wastewater with sewage disposal system.