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This article reviews the influencing factors of intraoperative pressure injury and the progress of preventive nursing. This paper provides reference and guidance to reduce the incidence of intraoperative pressure injury, improve patient comfort, reduce medical costs, and ensure patient nursing safety. (本文就术中压力性损伤发生的影响因素及预防护理进展进行了综述, 以期为降低术中压力性损伤的发生率、提高患者舒适度、降低医疗费用、保障患者护理安全提供参考和指导。)

Grouting with cementitious materials is a commonly-recognized measure to control the freezing and thawing deformation of artificial freezing strata. This study investigated the unfrozen water content of silty clay with different cement content under freeze-thaw condition, as well as the pore characteristics of the silty clay before and after freeze-thaw cycle based on nuclear magnetic resonance. It analyzed pore characteristics variation patterns of cement improved soil before and after freeze-thaw cycle and the micro-mechanism of freeze-thaw damage through scanning electron microscopy and mercury intrusion porosimetry. Results showed that: ①With the same water content, the increase of cement content would lead to the initial increase and subsequent decrease in the sensitivity to temperature of water molecule magnetization in the pores. ②When the cement content is between 0%~10% and at the same temperature during thawing process, the increase of cement content would lead to the initial decrease and subsequent increase of the unfrozen water content in the frozen soil. ③Compared with the silty clay without cement, cement improved silty clay shows little changes in its pores before and after the freeze-thaw cycle. The pore characteristics and microstructure of improved silty clay with cement content of 5% are less affected by freeze-thaw cycle. This research can provide references for the study of freeze-thaw resistance of improved soil and the stability control of strata frost heave and thaw settlement in artificial frozen engineering.

When traditional methods are used to test soil moisture migration of rock and soil, the undisturbed soil is often broken and reshaped, which will change the structure of rock and soil and affect the authenticity of the test results. In order to solve this problem, a new testing method is proposed by using the characteristics of nuclear magnetic resonance(NMR)technology for nondestructive measurement of moisture in materials. Firstly, the calibration experiment was carried out to establish a functional relationship between the NMR signal amplitude and the position of a soil sample with unit water mass in a non-uniform magnetic field of 0~0.05 T. Second, a one-dimensional infiltration experiment and NMR test were conducted to record the infiltration time, water mass increase and NMR signal under different test positions. Then, using the functional relationship obtained in the calibration experiment, approximations of the moisture mass and its spatial distribution in the sample were obtained by comparing the theoretical signal and the measured signals. Finally, the mudstone sample was cut into several parts to perform a verification experiment by oven drying, and the results showed that the error in water content was 4.05 % or less.

For the adhesion of polyethylene composite tape heat wound on the anticorrosion coating of bends for 3PE straight pipe, the difference of adhesion performance in different positions of bends was systematically studied, and the influence laws of test temperature and hot water immersion aging on adhesion performance degradation of the anticorrosion coating were analyzed. The results show that the adhesion performance of bend coating in different areas varies greatly. With the increase of test temperature, the peel strength between the anticorrosion coating and pipe body decreases gradually, and the peel strength between the layers of heat wound composite tape is slightly lower than that of FBE underlying. Besides,with the increasing of immersion period in hot water at 50 ℃, the adhesion performance between the anticorrosion coating and the pipe is stable with slight fluctuations in the initial stage(0-60 d), and then decreases rapidly(60-120 d). Moreover,suggestions were put forward to improve the undulating anticorrosion surface in the lap zone, the air bubbles trapped in the middle of the anticorrosion coating and the hollowing in the weld zone, etc. Generally, the research results are of great reference significance for the safe service of anticorrosion coating of pipelines.

The oxidation kinetics and film structure of two kinds of 310S heat-resistant steels (1# and 2#) with different grain sizes and composition at 800-1100 ℃ were studied by static oxidation discontinuous mass gain method. The differences of oxidation properties between the two steels were compared, and the growth mechanism of oxide film and the reasons for the differences were clarified. The results show that the oxide film is composed of Si-rich oxide layer and Cr-rich oxide layer and the oxidation rate of sample 1# is lower at 800-900 ℃; Cr-Mn oxide layer is added to the oxide film at 1000 ℃ and is transformed into Cr-Mn-Fe oxide layer at 1100 ℃, and their oxidation rates are similar; on the whole, the oxide film of sample 2# is denser, smoother, more adherent and more protective at all temperatures. Particularly, the spinel layer and the chromium oxide layer of the two are greatly different in the form at 1100 ℃, and the form of the oxide film of sample 2# is more conducive to long-term oxidation resistance. In general, the oxidation resistance of sample 2# is better than that of sample 1#. The smaller average grain size and more uniform grain of sample 2# improve the diffusion flux of preferred oxidation elements and reduce the uneven growth of oxide film, resulting in the differences of oxidation properties between the two.

The microstructure of Sn35Bi-xCo(x=0%, 0.3%, 0.7%, 1.0%, 1.2%, 1.5%, mass fraction) composite solder/Cu joints was observed by scanning electron microscopy (SEM).Combined energy spectrum (EDS) and XRD analysis, the difference of joint structure was studied. The mechanical properties of joints were tested by universal testing machine, and the influence mechanism of Co particle content on the structure and properties of SnBi/Cu joints was studied. The results show that, with the increase of Co particle content, the wettability of Sn35Bi-Co composite solder increases first and then decreases. When Co particle content is 0.7%, the wettability is the best.When appropriate amount of Co particles is added to the Sn35Bi/Cu joint in the solidification stage, the weld microstructure can be effectively refined, the IMC layer of the interface is more flat, Co atoms in the weld replace Cu atoms in the interface Cu6Sn5 layer, and the (Cu, Co)6Sn5 solid solution can be formed, which can strengthen the IMC layer of the interface.The shear strength of Sn35Bi-Co/Cu joints increases first and then decreases with the increase of Co particle content. When Co particle content is 0.7%, the maximum value of 54.09 MPa is obtained.

In order to study the energy absorption and transformation characteristics of marble, the release of strain energy and dissipation mechanism during creep process, this paper tested the stress-strain relationship of marble under uniaxial cyclic loading and multi-level creep cyclic loading respectively, and calculated their elastic energy density curves.The power function is used to fit the relationship between elastic energy density and stress of marble.By comparing the test data of the two loading modes, the results showed that the elastic energy density curves of uniaxial cyclic loading and multi-level creep cyclic loading were basically coincident, and they have the same elastic energy density curves, which means neither the creep loading mode nor the uniaxial cyclic loading mode will affect the elastic energy density curve of the marble.Comparing the ratio of elastic energy to external power in two loading modes, the results showed that the marble materials all went through three stages: compaction, stabilization and deterioration.After creep cyclic loading, the elastic energy storage capacity of marble would decrease to 43 % of uniaxial cyclic loading.Correspondingly, its strength also decreased obviously, which was 62 % of uniaxial cyclic loading.If the long-term bearing issue of this kind of marble is taken into account, the maximum stress value should be controlled below the stress that corresponds to the end point of the compaction stage of material.

When shield machine is driving for a long distance, it is often forced to stop due to obstacles or excessive wear of tools, which is one of the main risks of shield construction. In order to summarize the research progress of shield opening technology in urban metro, the paper systematically summarizes the two technical ideas of normal pressure opening and pressurized opening, and summarizes the principle, risk factors and principles of shield opening under two technical conditions. Combined with typical engineering examples, the application scope, key technology, advantages and disadvantages of conventional compressed air and saturated gas method with pressure opening technology are analyzed and summarized. The engineering application of atmospheric pressure opening technology and atmospheric pressure cutter disc tool changing technology for soil grouting and freezing reinforcement is summarized. Finally, combined with the current research progress and the development trend of large diameter underwater shield in China, the paper analyzes the technical challenges faced by the shield opening in the future, discusses the direction of further research, and provides a reference for the development of shield opening technology in China.

BackgroundThe passive residual heat removal (PRHR) system is an important innovative design of the advanced pressurized water reactor technology. Under accident conditions, PRHR system can transport decay heat in the form of natural circulation to ensure core cooling. However, the heat exchange function of PRHR system will be lost when the PRHR pipeline breaks. With development of the accident process, the coupling effect between different safety equipments of the passive core cooling system (PXS) will be affected. Besides, thermal hydraulic state of the reactor coolant system (RCS) will also be affected via complex interaction mechanism. As a result, the new thermal hydraulic phenomena occur, and thus ultimately affecting the accident mitigation capacity of the PXS.PurposeThis study aims to confirm the safety characteristics of PXS and identify the new thermal hydraulic phenomena of advanced passive nuclear power plant during accident with multiple failures.MethodsA series of integral effect tests of loss of coolant accident (LOCA) were conducted on the advanced core-cooling mechanism experiment (ACME) facility. The influence of failure of PRHR HX flow and heat exchanging function on LOCA accident process were investigated on the basis of the test cases including PRHR pipeline break and cold leg (CL) break. The unique thermal hydraulic phenomena occurred during PRHR LOCA were explored, and their influence laws on the coupling effect among PXS safety equipments, and the influence laws on thermal hydraulic state of RCS were obtained.ResultsThe results show that there is a momentary reverse flow and heat transfer process in PRHR HX at the beginning of PRHR LOCA compared with typical CL LOCA. Besides, the natural circulation process between the core and steam generators (SGs) plays a critical role in cooling and depressurization of RCS, and its corresponding time-averaged heat transfer power is increased by about 30%. Besides, the asymmetric arrangement of PXS leads to a significant difference of transient thermal hydraulic state between the RCS branches, namely the PRHR cools the coolant via one RCS loop while two core makeup tanks (CMTs) inject the cold water to the core via the other RCS loop, and the pipeline resistance distribution shows a significant impact on the injection performance of safety equipment with low driven head such as CMTs.ConclusionsThe unique and important thermal hydraulic phenomena in the early stage of the accident, namely reverse flow and heat transfer process in PRHR HX and natural circulation process between core and SGs, are identified. The asymmetric arrangement effect will be more noticeable when the break occurs in PRHR pipeline.

Aiming at the problems of structural dimension deviation, initial cracks and apparent defects in beam-column and other structures that occurred during the construction by Pile-Beam-Arch(PBA)approach, Based on the stochastic medium theory, a theoretical analysis model of the space-time effect of group tunnels excavation is established. The causes for the deviation of the building arches caused by the asymmetric construction are analyzed. Taking asymmetric excavation of 8 pilot tunnels in a typical PBA station as an example, the mechanism of uneven changes in stratum space caused by multi-step construction of pilot tunnels in large-span cross-section tunnels is researched. The essential cause of the deviation of the building arches is analyzed, and the deformation law of the surface settlement trough spatial shape swinging left and right with the excavation of the guide tunnel is reconstruced. According to the above research, it is pointed out that the arching being closed and looped, the rapid synchronization operation, the side hole divided into span building arches and construction optimization to achieve symmetric synchronization are the main countermeasures to eliminate or reduce the deviation of building arches.

The rock mechanism under frozen condition has played down the significance on the design of frozen wall thickness and section height of the ultra-deep shaft in Western of China.This paper investigated the particle size and voids distribution principles using magnified image technique, which is on the typical medium size sandstone within the deep water-rich stratum during a coal mining construction with artificial freezing skill in Ordos of China.The frozen medium size sandstone have been studied with triaxial compression test under the temperature of-5℃,-10℃,-15℃, and Brazilian Split test at 26℃,-10℃ and-20℃.The test results indicated that the compressive strength improved linearly up to maximum of 27.29%when temperature dropped down, and this effect was weakened with the increase of the confining pressure.So did the internal frictional angle and cohesion, which ended up with the biggest rise of 12.54%and 18.69%.The tensile strength jumped from 0.73 MPa at 26℃ up to 1.59 MPa at-10℃, as of 118.18%extra, followed with declining when the temperature reduced more.The strength property of medium sandstones have been further improved with only cer-tain extent during lowering the temperature, therefore the design criteria of frozen wall thickness should rather be governed by the purpose of sealing water than over cooling control.

Eleven kinds of chiral compounds have been well separated within 10 min on polysaccharide derivative-based chiral stationary phases named Chiralpak IA, IB, IC, ID, IE and IF by supercritical fluid chromatography (SFC). The chiral recognition of these chiral compounds has demonstrated good complementary enantioselectivities of the six chiral columns, which were proved to be useful for chiral SFC. Both the elution time and enantioselectivies could be significantly affected by the modifier types and their concentrations, such as methanol, ethanol and isopropanol, which should be optimized during the experiments. In addition, the solvent versatility of the immobilized chiral stationary phase on the optimization of the chiral separation was helpful.

In a pot experiment, axenic pomelo (Citrus grandis cv. Changshou Shatian You) seedlings were inoculated with arbuscular mycorrhizal (AM) fungi Gigaspora margarita, Glomus mosseae and Glomus versiforme, respectively, and their vegetative growth and mineral contents were studied. The results showed that the seedlings inoculated with test AM fungi could be infected effectively, and their shoot and root growth, especially fibrous root growth, was significantly improved, compared with the control. After inoculated with G. mosseae, the root length, lateral root number, and fibrous root number and length of the seedlings were increased by 22.7%, 35.7%, 160. 8% and 103.2%, respectively. The inoculation of these three AM fungi could significantly elevate the N, P, K, Ca, Mg, Zn, Cu and Mn contents in seedlings leaves. For example, the P content was increased by 46.8%, 88. 7% and 32. 3% , respectively, compared with the control. Among the three treatments, the seedlings inoculated with G. mosseae had the best vegetative growth, and the highest mycorrhizal dependence and N, P, K, Ca, Zn and Cu contents. The relative occurrence of AM fungal species decreased in the order of G. mosseae > G. margarita > G. versiforme, indicating that G. mosseae was most suitable for C. grandis seedlings inoculation.

Objective: To investigate the changes and of nuclear factor-kappa B (NF-kappaB) and intercellular adhesion molecule (ICAM)-1 expression in airway epithelial cells from smoking rats., Methods: Wistar rats (n = 39) were randomly divided into a nonsmoking control group and 2 smoking groups-smoking for 1 month and 3 months, with 13 rats in each group. Immunohistochemistry and in situ hybridization staining were used to semiquantitatively analyse the changes of NF-kappaB and ICAM-1 expression in airway epithelial cells., Results: (1) The percentages of positive cells for NF-kappaB nuclear staining in bronchiolar epithelial cells in 1 month smoking group (63 +/- 4)% and 3 month smoking group [(51 +/- 5)%] were significantly higher than that in the control group [(27 +/- 5)%] (P < 0.01 respectively). (2) ICAM-1 mRNA expression in bronchial and bronchiolar epithelial cells in the 1 month smoking group (0.645 +/- 0.038, 0.747 +/- 0.041) and the 3 month smoking group (0.688 +/- 0.062, 0.809 +/- 0.023) was significantly higher than those in the control group (0.526 +/- 0.023, 0.635 +/- 0.044), (P < 0.01 respectively), and the expression of ICAM-1 mRNA in the 3 month smoking group was higher than that in the 1 month smoking group (P < 0.05 and P < 0.01 respectively). (3) ICAM-1 protein expression in the main bronchial and bronchiolarepithelial cells in the 1 month smoking group (0.73 +/- 0.04, 0.94 +/- 0.05) and the 3 month smoking group (0.77 +/- 0.04, 0.99 +/- 0.03) was significantly higher than those in the control group (0.57 +/- 0.04, 0.83 +/- 0.04) (P < 0.01 respectively), and the expression of ICAM-1 protein in the 3 month smoking group was higher than those in the 1 month smoking group (P < 0.05 respectively). (4) ICAM-1 mRNA and protein expression in bronchioles were significantly higher than those in the bronchi (P < 0.01 respectively) in all groups. (5) The percentage of cells staining positive for nuclear NF-kappaB correlated with ICAM-1 protein expression in bronchioles from the 1 month smoking group (r = 0.462, P < 0.05)., Conclusion: NF-kappaB and ICAM-1 may play an important role in smoking-induced airway inflammation.