Subjects: Geosciences >> Geography submitted time 2024-03-01 Cooperative journals: 《干旱区研究》
Abstract： Mastering the regional wind sand movement environment and sediment particle size characteristics isthe key to studying wind sand flow, and is of great significance for the prevention and recovery of regional windsand disasters. Based on the wind regime data of Wuzhumuqin Sandy Land, this paper studies the variationcharacteristics of sand driving wind regime and sand transport potential, and reveals the spatial differences ofsand environment in this area by combining with the sediment particle size data. The results show that:（1）Theannual average frequency of sand blowing in the Wuzhumuqin sandy land is 33.8%, with an average wind speedof 3.34-5.40 m·s-1, and an average sand blowing wind speed of 6.46-8.49 m·s-1. The frequency and wind speedof sand blowing in the north of the sandy land are greater than those in the south, and those in the west are greaterthan those in the east.（2）The overall annual frequency and wind speed of sand storms are the highest in spring.The wind direction of sand storms is mainly in the southwest direction, and the frequency in the WSW directionis the highest. （3）The sand transport potential in the sandy land is 19.2-193.7 VU, which is generally a low windenergy environment. The wind conditions are mostly sharp bimodal wind conditions. The sand transport potentialin the north of the sandy land is greater than that in the south, and that in the west is greater than that in the east.Throughout the year, sand material is transported to the east and northeast, and spring is the most importantperiod of wind sand activity.（4）The sandy land is mainly composed of coarse and medium sand components,with soil particle sizes in the south and west being coarser and finer in the east. The sorting of sediment in thenorthern and eastern parts of the sandy land is poor, and the particle size components are greatly influenced byexternal factors. Overall, the sandstorm activity in the northern part of the sandy land is the strongest, making itsuitable for artificial planting or laying sand barriers to fix sand. Protection forest is planted in the east of thesandy land to avoid the continuous eastward movement of sand.
Subjects: Library Science，Information Science >> Library Science submitted time 2023-05-11
Abstract： Purpose/Significance This paper puts forward the experience of Tsinghua University Library in electronic resource management and quality control based on ALMA system, which can provide reference for the application practice of peer libraries in the next generation library service platform and the method of electronic resource data quality control. Method/Process The necessity of data quality control of electronic resources was proposed through literature research; This paper adopted the method of questionnaire to investigate the electronic resource management mode and predicament of peer libraries, and extracted common problems. Based on the data model, workflow and management mode of electronic resource management in ALMA system, this paper put forward corresponding data quality control methods from the electronic resource library and single volume level, bibliographic level, discovery system and central discovery index level, providing reference for data quality control in the process of electronic resource management. Result/Conclusion Electronic resource management is a complex and multi-platform system project. The library should develop multi-level and three-dimensional data quality control scheme, and improve the electronic resource management and service level.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract： The interface character and corrosion resistance of SiCp/Al composites prepared with electroless nickel plated SiC particles were studied by means of XRD, SEM and EDS as well as polarization curve and electrochemical noise test. The results show that the nickel plating improves the wettability between SiC particles and aluminum matrix, increases the interface bonding strength and reduces the formation of Al4C3, the later is a detrimental product resulted by the interfacial reaction of SiC and the matrix. SiCp/Al composites made of non- modified SiC particles suffered from local corrosion during immersion in 3.5%NaCl solution for the first 2000 s, and then turn to uniform corrosion. However, SiCp/Al composites made of Ni-plated SiC particles suffered from local corrosion during the whole immersion test. In addition, the Ni-plated SiCp/Al composites exhibited much positive free corrosion potential and higher noise resistance, therefore, implying a better corrosion resistance.
Subjects: Mechanics >> Oscillation and Wave submitted time 2022-12-21 Cooperative journals: 《应用力学学报》
Abstract：
The QZSID system consisting of parallel Quasi-Zero-Stiffness(QZS),damper and inerter is studied.In order to study the dynamic response mechanism of QZSID isolation system under near-fault vertical earthquake,an analysis model of QZSID system under vertical earthquake is established.The response control effect of QZSID isolation system is analyzed by nonlinear time-history response.The results show that the seismic response control effect of inerter is related to predominant period of near-fault vertical earthquakes.The inerter has a good control effect on the acceleration of long-period near-fault earthquakes.However,there is a poor control effect on the displacement.Although the resonance period is not prolonged under the action of long-period ground motion,the system can avoid the resonance frequency of ground motion.The system can still obtain good isolation effect.The vertical natural vibration period of the system should not be too large.The damping ratio and static equilibrium height can be helpful to the seismic response control of the system.Seismic responses are not proportioned to the mass parameters of inerter.The isolation effect of the inerter is related to the characteristics of ground motions.
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology submitted time 2020-04-26 Cooperative journals: 《干旱区研究》
Abstract：为了探究西鄂尔多斯地区荒漠灌丛的光合生态适应性，以4种天然荒漠灌丛半日花(Helianthemum songaricum)、红砂(Reaumuria songarica）、沙冬青(Ammopiptanthus mongolicus )、霸王(Sarcozygium xanthoxylon）为研究材料，利用Li-6400便携式光合测定仪野外原位测定荒漠灌丛日光合动态和季节动态规律。结果表明：① 不同季节灌丛光合作用适宜的温度存在差异，高温环境使灌丛净光合速率最适温度升高，低温环境使其降低。② 不同季节4种灌丛的净光合速率、蒸腾速率、水分利用效率和气孔导度日变化曲线趋势为“双峰形”，胞间CO2浓度日变化曲线趋势为“W形”，但不同季节各指标平均日变化趋势表现各异。③ 不同季节灌丛净光合能力表现为：沙冬青>霸王>红砂>半日花，说明沙冬青具有较强的生态适应性。④ 净光合速率和蒸腾速率日变化趋势几乎保持同步状态，表明4种灌丛叶片气孔对外界环境变化反应敏感。⑤ 水分是限制荒漠灌丛生长发育的关键因素。为了保证荒漠植物的群落稳定性和生物多样性，在夏、秋季需对沙冬青、半日花、红砂和霸王进行水分管理。
Subjects: Biology >> Zoology submitted time 2018-12-25 Cooperative journals: 《动物营养学报》
Abstract：磷是参与动物机体多种生物学反应的必需元素之一，但畜禽养殖，尤其是反刍动物养殖过程中磷排泄带来的水体污染等环境问题已经成为业界关注的焦点，因此如何提高磷的利用率、减少磷排泄是行业亟待解决的问题。本文总结了反刍动物磷利用的相关研究进展，并结合其代谢特点归纳了提高磷利用率的措施，提出了下一步研究的方向。
Subjects: Biology >> Zoology submitted time 2018-12-24 Cooperative journals: 《动物营养学报》
Abstract：本试验旨在研究维生素A对奶牛乳腺上皮细胞（BMECs）内乳脂和乳蛋白合成相关基因表达的影响。采用单因素完全随机试验设计，将第3代BMECs随机分为6个处理，每个处理6个重复，使用无血清培养基饥饿24 h后，采用维生素A浓度分别为0（对照）、0.05、0.10、0.20、1.00和2.00 μg/mL的培养基培养24 h。结果表明：与对照组相比，1.00、2.00 μg/mL维生素A可以显著提高相对增殖率以及甘油三酯（TG）含量（P<0.05）；维生素A能显著提高乳脂合成相关基因过氧化酶体增殖物激活受体γ（PPARG，0.05、0.10、0.20、1.00和2.00 μg/mL）、固醇调节元件结合蛋白1（SREBP1，0.05、0.10 µg/mL）、硬脂酰辅酶A去饱和酶（SCD，0.05、0.10 µg/mL）的基因表达量（P<0.05）；维生素A也能显著提高乳蛋白合成相关基因信号转导转录激活因子5（STAT5，0.20 μg/mL）、αs1-酪蛋白（CSN1S1，0.05和0.10 μg/mL）、κ-酪蛋白（CSN3，0.10 μg/mL）基因表达量（P<0.05）；维生素A也能显著提高乳脂合成相关酶乙酰辅酶A羧化酶（ACACA）活性（0.05、0.10、0.20和1.00 μg/mL）（P<0.05）。结果提示，维生素A对BMECs内乳脂、乳蛋白合成相关基因表达的促进效果呈浓度依赖性，以0.10 μg/mL维生素A效果较好
Subjects: Biology >> Zoology submitted time 2018-12-20 Cooperative journals: 《动物营养学报》
Abstract：本试验旨在研究不同无机磷源对断奶仔猪钙、磷表观消化率及钙、磷代谢的影响。试验选取200头遗传背景一致、健康状况良好、初始体重为（8.41±0.97） kg的（28±2）日龄的长×大断奶仔猪，随机分成5个组，每个组4个重复，每个重复10头仔猪（公母各占1/2）。5组仔猪分别饲喂含0.66%粉状磷酸氢钙（DCP）、0.44%粒状磷酸二氢钙（MCP）、0.44%粉状MCP、0.49%粉状磷酸一二氢钙（MDCP）、0.49%粒状MDCP的饲粮，并保持饲粮钙、磷水平一致。试验期28 d。结果显示：1）各组仔猪的钙和干物质表观消化率差异不显著（P>0.05），粉状MDCP组仔猪的磷表观消化率显著高于粉状DCP、粒状MCP和粉状MCP组（P0.05）；2）仔猪血清钙、磷含量各组之间差异不显著（P>0.05），但粉状MCP组仔猪血清碱性磷酸酶活性显著低于其他组（P0.05），但粉状MDCP、粉状MCP以及粒状MCP组蹄骨钙含量显著高于粉状DCP组（P<0.05）。由此可知，相较于粉状DCP，粉状MDCP、粒状MDCP、粒状MCP和粉状MCP均能较好地促进断奶仔猪钙、磷的代谢和利用，是替代粉状DCP的良好磷源。
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-05-20 Cooperative journals: 《计算机应用研究》
Abstract： Based on understanding of theory and practice, Handle System will coexist with the Domain Name System for a long time in the future, however, resolution protocols and identifier code rules of two identifier resolution system are incompatibility, leading to a barrier between data space of them. Therefore, it is urgent for us to resolve the connectivity problem of two identifier resolution system currently. By analyzing pros and cons of existing solutions, we found that the separation of protocol data unit and protocol can solve the incompatibility problem of resolution protocol and identifier code rule of two systems. Based on such a separation mechanism, inter-operation mechanism of Handle System and Domain Name System based on the proxy server was developed. Simulation experiments show that compared with traditional client-server ones, the response time of this new mechanism increases a little and is within the acceptable range.
Subjects: Medicine, Pharmacy >> Preclinical Medicine submitted time 2017-12-27 Cooperative journals: 《南方医科大学学报》
Abstract： Objective To explore the relationship of gentamicin-induced cochlear damage with autophagy-related protein LC3, beclin1, Na+-K+-2Cl- cotransporter (NKCC1) mRNA and endothelin-1 (ET-1), and investigate the protective mechanism of PPTA against gentamicin-induced cochlear damage. Methods Sixty guinea pigs were randomly divided into control group (with saline and artificial perilymph injections), model group (with gentamicin and artificial perilymph injections), concurrent treatment group (with gentamicin and PPTA injections), model control group (with artificial perilymph injection 7 days after gentamicin injection) and delayed treatment group (with PPTA injection 7 days after gentamicin injection). Saline and gentamicin (160 mg/kg) were injected intraperitoneally, and artificial perilymph and PPTA were injected into the otocysts on a daily basis for 7 consecutive days. Hearing impairment of the guinea pigs was analyzed with ABR, and the protein expressions of beclin1 and LC3 in cochlear tissue were tested. The expression of NKCC1 mRNA was detected with RT-PCR, and the expression of ET-1 was detected immunohistochemically. Results The ABR thresholds in the model group and model control group were similar (P>0.05) , but significantly higher than those in the other 3 groups (P<0.05); the threshold was significantly lower in concurrent treatment group than in delayed treatment group (P<0.05). Compared with those in the other 4 groups, the expressions of LC3 II, beclin1, and NKCC1 mRNA were significantly increased in the model group (P<0.05); and those in delayed treatment group were significantly lower than those in the model control group (P<0.05). The expressions of ET-1 in the Corti organ, striavascularis and spiral ganglion were significantly higher in the model group but significantly lower in the control group than those in the other 4 groups; ET-1 expression was significantly lower in delayed treatment group than in the model control group. Conclusion PPTA offers protection against gantamicin-induced cochlear damage in guinea pigs by inhibiting cell autophagy and suppressing of NKCC1 and ET-1 expressions. Early intervention with PPTA produces better therapeutic effect, suggesting that gantamicin causes irreversible injury of the auditory cells.
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