Numerical Simulation and Experimental Validation of Squeeze Casting of AlSi9Mg Aluminum Alloy Component with a Large Size

The squeeze casting process for an AlSi9Mg aluminum alloy flywheel housing component was numerically simulated using the ProCAST software, and orthogonal simulation tests were designed according to the L16 (4) ⁵ orthogonal test table to investigate the alloy melt flow rule under four factors and four levels each of the pouring temperature, mold temperature, pressure holding time and specific pressure, as well as the distributions of the temperature fields, stress fields and defects. The results showed that the flywheel housing castings in all 16 test groups were fully filled, and the thinner regions solidified more quickly than the thicker regions. Hot spots were predicted at the mounting ports and the convex platform, which could be relieved by adding a local loading device. Due to the different constraints on the cylinder surface and the lower end surface, the solidification was inconsistent, the equivalent stress at the corner junction was larger, and the castings with longer pressure holding time and lower mold temperature had larger average equivalent stress. Shrinkage cavities were mainly predicted at mounting ports, the cylindrical convex platform, the peripheral overflow groove and the corner junctions, and there was also a small defect region at the edge of the upper end face in some test groups.     

Thoughts on how to think (and talk) about RNA structure

Recent events have pushed RNA research into the spotlight. Continued discoveries of RNA with unexpected diverse functions in healthy and diseased cells, such as the role of RNA as both the source and countermeasure to a severe acute respiratory syndrome coronavirus 2 infection, are igniting a new passion for understanding this functionally and structurally versatile molecule. Although RNA structure is key to function, many foundational characteristics of RNA structure are misunderstood, and the default state of RNA is often thought of and depicted as a single floppy strand. The purpose of this perspective is to help adjust mental models, equipping the community to better use the fundamental aspects of RNA structural information in new mechanistic models, enhance experimental design to test these models, and refine data interpretation. We discuss six core observations focused on the inherent nature of RNA structure and how to incorporate these characteristics to better understand RNA structure. We also offer some ideas for future efforts to make validated RNA structural information available and readily used by all researchers.     

Application of Iron Tailings-Based Composite Supplementary Cementitious Materials (SCMs) in Green Concrete

How to treat the iron tailings of mining solid waste with high value is an urgent problem on a global scale. In recent years, the application of iron tailings in the building materials industry has attracted the attention of many scholars. The conversion of iron tailings into green building materials helps achieve carbon neutrality and high-value utilization of solid waste, and promotes sustainable development. Although iron tailings have been extensively studied as supplementary cementitious materials, the performance of concrete is not ideal due to its low activity. In this study, the hybrid supplementary cementitious materials system was prepared by iron tailings, phosphorus slag, and steel slag, and the effects of supplementary cementitious materials type, iron tailings content, iron tailings grinding time, and supplementary cementitious materials content on concrete performance were studied. The compressive properties, iron tailings properties, pore structure, interfacial transition zone, and element distribution of hydration products of concrete were tested by compressive strength tests, X-ray Diffractometer (XRD), X-ray Photoelectron Spectroscopy (XPS), Mercury Intrusion Porosimetry (MIP), Backscattering Electron Tests (BSE), and Energy Dispersive Spectrometer (EDS). The results show that further grinding improves the iron tailings activity. There is a synergistic mechanism between steel slag and phosphorus slag in the composite supplementary cementitious materials, which overcomes the low activity defect of iron tailings and produces concrete with a compressive strength exceeding 40 MPa. The composite supplementary cementitious materials can optimize the interfacial transition zone of the concrete interface and reduce the calcium–silicon ratio of the hydration products. However, it will deteriorate the pore structure of the concrete matrix, cause part of the concrete matrix to be damaged and lead to a loss of compressive strength, and the loss is acceptable. This work broadens the methods of comprehensive utilization of iron tailings and also provides a reference for a more detailed understanding of the properties of iron tailings-based concrete.     

Treatment of secondary pneumothorax with interstitial lung disease: the surgical indications at the start of treatment is important

BackgroundSecondary pneumothorax with interstitial lung disease (ILD) is often difficult to treat in comparison to primary pneumothorax. The purpose of this study was to analyze the actual management and outcome, and to find the most effective treatment.MethodsAmong 180 patients with pneumothorax caused by ILD, who were managed between January 2000 and April 2021, 129 patients were included. Fifty-one patients with observation only were excluded. In the present study, a patient was considered to be cured if their chest tube could be removed.ResultsThe managements included chest tube drainage alone (n=41), pleurodesis (n=67), bronchoscopic treatment (n=14), and surgery (include overlapping cases) (n=25). The mean number of pleurodesis treatments was 2.4 (range, 1–9), and the most frequently used agent was blood-patch. All patients who received bronchoscopic treatment underwent bronchial occlusion with silicon spigots. The surgical procedures included bullectomy (n=20), lung cyst ligation (n=3), pleural covering with oxidized cellulose sheet (n=1), and spraying of fibrin glue alone (n=1). One hundred patients (77.5%) were curatively treated, 27 patients (20.9%) died, and 2 patients were transferred without chest tube removal. Among 25 patients who received surgery [including 6 patients with performance status (PS) ≥2], 24 patients (96.0%) were cured, and 1 patient died due to an acute exacerbation of ILD after surgery. The univariate analysis revealed that PS ≥2 and >3 pleurodesis treatments were significant non-curative factors, while steroid treatment before the development of pneumothorax was not.ConclusionsThe outcomes of surgery for pneumothorax in patients with ILD were good, and it is desirable to consider the surgical indications.     

以教学评估为契机培养高素质的药学人才

为迎接教学评估,培养高素质的药学人才,药学教学应从更新观念,加快师资队伍建设,改进人才培养模式,教学方法等方面入手。     

Study on Remote Field Eddy Current Testing Technology for Crack-like Defects in Long Truss Structure of Aircraft

Detection of hidden defects of aircraft long truss structures (aluminum alloy) is a challenging problem. The shape of the aircraft truss structure is complex, and the crack defects are buried in a large depth. Without the restriction of skin effect, remote field eddy current (RFEC) has great advantages in detecting buried depth defects. In this paper, in order to detect the hidden defects of the aluminum alloy aircraft long truss structure, the remote field eddy current probe is improved from two aspects of magnetic field enhancement and near-field signal suppression using the finite element method. The results show that indirect coupling energy is greatly enhanced when the connected magnetic circuit is added to the excitation coil. By adding a composite shielding structure outside the excitation coil and the detection coil, respectively, the direct coupling energy is effectively restrained. As a result, the size of the probe is reduced. By optimizing the coil spacing and probe placement position, the detection sensitivity of the probe is improved. The simulation is verified by experiments, and the experimental results are consistent with the simulation conclusions.     

外科治疗颞叶继发性癫痫的临床分析

目的 探讨颞叶继发性癫痫的原因并总结手术治疗经验。方法 对我院自1994年1月至2002年12月手术治疗的26例颞叶继发性癫痫患者的临床资料进行回顾性分析。手术方式是在皮层脑电图(ECoG)监测下采用病灶切除、病灶周致痫皮质切除、前颞叶切除和病灶周围皮质区多处软膜下横纤维切断等多种方法的组合。结果 26例病人无手术死亡及并发症。23例病人随访3个月∽7年，症状完全消失者16例(占69．6％)，术后癫痫发作显著减少者(发作频率不到原来的25％)5例(21．7％)。术后癫痫发作减少者(发作频率不到原来的50％)2例(8．7％)。结论 多种手术方法结合治疗颞叶继发性型癫痫患者安全有效。