Microstructure evolution,mechanical properties and fracture behavior of Al-xSi/AZ91D bimetallic composites prepared by a compound casting

In this paper,the effect of the Si content on microstructure evolution,mechanical properties,and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically.The obtained results showed that all the Al-xSi/AZ91D bimetallic composites had a metallurgical reaction layer(MRL),whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites,while the hypereutectic Al-Si/AZ91D composites were opposite.The MRL included eutectic layer(E layer),intermetallic compound layer(IMC layer)and transition region layer(T layer).In the IMC layer,the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg_(2)Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites.Besides,increasing Si content,the thickness proportion of the T layer increased,forming an inconsistent preferred orientation of the MRL.The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content,and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa,which was 73.4% higher than the Al-6Si/AZ91D composite.The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content.The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg_(2)Si particle reinforcement,the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.

A low-frequency and broadband wave-insulating vibration isolator based on plate-shaped metastructures

A metamaterial vibration isolator,termed as wave-insulating isolator,is proposed,which preserves enough load-bearing capability and offers ultra-low and broad bandgaps for greatly enhanced wave insulation.It consists of plate-shaped metacells,whose symmetric and antisymmetric local resonant modes offer several low and broad mode bandgaps although the complete bandgap remains high and narrow.The bandgap mechanisms,vibration isolation properties,effects of key parameters,and robustness to complex conditions are clarified.As experimentally demonstrated,the wave-insulating isolator can improve the vibration insulation in the ranges of[50 Hz,180 Hz]and[260 Hz,400 Hz]by 15 dB and 25 dB,respectively,in contrast to the conventional isolator with the same first resonant frequency.

新西兰乳制品法规标准监管体系及其借鉴意义

新西兰是一个畜牧业极为发达的国家,其乳制品畅销全球,有着很好的声誉。这是因为新西兰不仅有丰富的原料乳资源,而且极其重视乳制品的安全管理。新西兰通过制定一系列标准法规,从牧草种植、饲料加工、奶牛养殖、生乳管理到乳制品生产加工的各个环节加强控制,从而保障乳制品的安全。本文介绍新西兰乳制品基本监管情况和贸易情况,并分析新西兰乳品行业创新技术对我国的借鉴意义。

进出口食品检验检疫合规要求及法律法规风险防范

我国进出口食品检验检疫的上位法规定主要包括《食品安全法》等进出口食品安全相关法律、《食品安全法实施条例》等行政法规以及《进出口食品安全管理办法》等部门规章。进出口食品安全监管制度着力从积极落实食品安全“四个最严”要求,通过进出口各参与方高度协作,针对进出口食品生产、贮存、运输和进出口活动方面,从事前、事中、事后角度加强管理,构建科学高效、协调公开的进出口食品安全现代化治理制度体系。

从沙门氏菌控制看丹麦食品安全监管

2024年3月至5月,丹麦发生了一起59人因食用进口碎肉而感染沙门氏菌的食品安全事件。本文围绕这一事件,详细阐述了丹麦食品安全主管部门为应对该事件而采取的处置措施。丹麦对沙门氏菌的控制措施主要来自于对养殖场源头的沙门氏菌基底监测和风险评估,这也是丹麦制定本国沙门氏菌控制技术规范的基础,而迅速且准确的疫情反应机制则是有效控制疫情传播并清除疫情的重要手段。

“印度—中东—欧洲经济走廊”计划评估

2023年9月,美国、印度及中东和欧洲多国出于对各自战略利益的考虑,联手推出建设“印度—中东—欧洲经济走廊”计划。该计划旨在整合走廊沿线的各种要素并建立协调实体,以解决走廊建设的技术、设计、融资、法律和相关监管标准等问题,通过加强亚洲、阿拉伯海湾、欧洲之间的互联互通和经济一体化来刺激经济发展,并显露出地缘战略意图。受地缘政治形势复杂多变、多国协调工作纷繁冗杂、项目建设资金筹措困难、美国总统大选前景不明等多重因素制约,“印度—中东—欧洲经济走廊”从规划到落地尚存在诸多不确定性。然而,若其成功实施,则可能对世界和地区局势产生重要影响,并给“一带一路”建设带来地缘竞争压力。鉴此,中国需予以妥善应对。

乌克兰危机后的东北亚地区安全形势

乌克兰危机爆发以来,东北亚安全不确定性增强。乌克兰危机推进了东北亚安全秩序重塑,呈现新旧秩序交替特征。从力量格局看,未来中美战略互动将对地区安全局势起到主导性作用,美日韩与美日台“三方安全合作”不断强化,美国对华“战略遏制”将会加强,东北亚周边安全挑战压力增大,摩擦增加并将呈现多发态势。

Preparation, interfacial regulation and strengthening of Mg/Al bimetal fabricated by compound casting: A review

Mg/Al bimetal combines the advantages of both aluminum and magnesium and has broad application prospects in automotive, aerospace,weapons, digital products and so on. The compound casting has the characteristics of low cost, easy to achieve metallurgical combination and suitable for the preparation of complex bimetallic parts. However, bimetallic joint strength is low due to differences of physical properties between Al and Mg, oxide film on metallic surface and interfacial Al-Mg IMCs, which is closely related to the interfacial microstructure and properties. Therefore, how to control the interface of the bimetal to achieve performance enhancement is the focus and difficulty in this field. At present, there are mainly the following strengthening methods. First, the “zincate galvanizing” and “electrolytic polishing+anodic oxidation” technology were exert on the surface of Al alloy to remove and break the oxide film, which improved the wettability between Al and Mg. Second, the undesirable Al-Mg IMCs were reduce or elimination by adding the interlayers(Zn, Ni and Ni-Cu). Thirdly, the evolution process of interfacial microstructure was changed and fine strengthening phases were formed by adding Si element to Al alloy or rare earth element to Mg alloy. Fourthly, mechanical vibration and ultrasonic vibration were applied in the process of the filling and solidification to refine and homogenize the interfacial structure. Finally, some other methods, including secondary rolling, thermal modification, heat treatment and constructing exterior 3D morphology, also can be used to regulate the interfacial microstructure and compositions. The above strengthening methods can be used alone or in combination to achieve bimetallic strengthening. Finally, the future development direction of the Mg/Al bimetal is prospected, which provides some new ideas for the development and application of the Mg/Al bimetal.

Effects of mechanical vibration on filling and solidification behavior, microstructure and performance of Al/Mg bimetal by lost foam compound casting

Al/Mg bimetal was prepared by lost foam solid-liquid compound casting,and the effects of mechanical vibration on the filling and solidification behavior,microstructure and performance of the bimetal were investigated.Results show that the mechanical vibration has a remarkable influence on the filling and solidification processes.It is found that after mechanical vibration,the filling rate increases and the filling rate at different times is more uniform than that without vibration.In addition,the mechanical vibration also increases the wettability between liquid AZ91D and A356 inlays.The mechanical vibration reduces the horizontal and vertical temperature gradient of the casting and makes the temperature distribution of the whole casting more uniform.Compared to the Al/Mg bimetal without vibration,the shear strength is improved by 39.76%after the mechanical vibration is applied,due to the decrease of the inclusions and Al_(12)Mg_(17) dendrites,and the refinement and uniform distribution of the Mg_(2)Si particles in the interface of the Al/Mg bimetal.

基于网络药理学的虎杖治疗结直肠癌作用机制研究

目的基于网络药理学方法分析虎杖治疗结直肠癌的药理机制,为新药研发提供参考。方法通过TTD、Dis数据库提取结直肠癌的主要靶点,从TCMSP数据库中提取虎杖的主要化学成分,以口服生物利用度(OB)≥30、药物半衰期(HL)≥4 h、类药性(DL)≥0.18筛选活性成分,通过HIT、ChemMapper、STITCH数据库提取活性成分主要靶点,采用Cytoscape3.2.1软件构建成分-靶点网络,并分析主要通路。结果经筛选,共获得9种主要活性成分,作用于56个靶点,其中核心靶点有ESR1、KRAS、TYMS、AKT1、PPARD、PTGS1、FNTB、PTGS2、PPARG、ALDH2、PDE5A等,主要作用于调控生长因子及其受体信号通路、白细胞介素介导的信号通路、细胞凋亡及生物氧化等多种信号通路。结论本研究初步揭示了虎杖治疗结直肠癌的多成分、多靶点、多通路的作用机制,可为虎杖开发利用提供参考。

基于数据挖掘探讨吴良村教授治疗原发性肝细胞癌的用药规律

[目的]探讨吴良村教授辨治肝细胞癌的用药规律,指导临床用药,提高中医药治疗肝癌的临床疗效。[方法]通过计算机和人工检索相结合,收集2014年01月01日～2017年01月01日期间吴良村教授在浙江省中医院门诊的肝细胞癌患者病案。将患者临床信息转化为有效数据表,对药物累计频数、药物性味、药物归经及其功效归类采用描述性分析,对频数最高的33种药物进行系统聚类分析。[结果]共纳入80例患者,共计160诊次及用药150种,累积用药2681次,其中使用频数最多者为枸杞子,其次为北沙参、甘草、茯苓、青蒿、黄芩、鸡内金。药性使用频次最多的为平性药,药味使用频次最多的为甘味药,归经使用频次最多的为足阳明胃经,药物种类使用频次最多的为补虚药。聚类分析结果最终将药物分为14类,涉及方剂有一贯煎,药对涉及青蒿和黄芩、茯苓和山药、白术和太子参、绿梅花和柴胡等,单药可见佛手、三叶青、白花蛇舌草。[结论]吴良村教授辨治肝细胞癌以一贯煎滋阴疏肝为主,随证辅以益气健脾、清利湿热、解毒抗癌、消食和中之法,临证用药多以甘、苦、平、寒性味为主。

注册制改革对IPO抑价的影响——来自创业板的证据

利用多元回归模型,分析注册制改革对创业板新股IPO抑价及短期收益的影响,以2009年10月30日至2021年3月31日在创业板上市的932家企业为研究样本进行实证检验,并以上市后前5个交易日抑价替代首日抑价进行稳健性检验,研究发现:创业板注册制改革红利的释放和投资者对改革的投机行为,显著提升了新股上市首日IPO抑价。创业板注册制改革的实施虽然没有抑制投资者的“炒新”行为,但促成了投资者投资行为的转变,使投资者更关注风险与收益的对比关系,投资更趋理性。创业板注册制改革的实施加快了新股价值的回归,表现为上市后前5个交易日抑价和新股短期收益的显著下降。另外,研究发现,承销商的作用并没有得到市场的显著认可。应全面贯彻“零容忍”方针,切实提高信息披露质量;加强对投资者的教育,提高投资者对注册制的适应能力;坚持从严监管,压实中介机构责任;做好顶层设计,确保全面注册制改革平稳落地。

从中医气血津液论述自噬治疗恶性肿瘤的理论依据

自噬作为细胞存活的机制,在肿瘤的发生发展及治疗上发挥着双重作用。肿瘤的发生是气血津液失调的结果,自噬的功能与中医气血津液密切相关。笔者通过从气、血、津液三方面辨析自噬治疗恶性肿瘤的病机特征,提出从气虚、气滞、瘀血、痰瘀毒结等论治,从而为自噬治疗肿瘤提供中医理论依据。

Application of neuroendoscopic surgical techniques in the assessment and treatment of cerebral ventricular infection

Cerebral ventricular infection (CVI) is one of the most dangerous complications in neurosurgery because of its high mortality and disability rates. Few studies have examined the application of neuroendoscopic surgical techniques (NESTs) to assess and treat CVI. This multicenter, retrospective study was conducted using clinical data of 32 patients with CVI who were assessed and treated by NESTs in China. The patients included 20 men and 12 women with a mean age of 42.97 years. NESTs were used to obliterate intraventricular debris and pus, fenestrate or incise the intraventricular compartment and reconstruct cerebrospinal fluid circulation, and remove artificial material. Intraventricular irrigation with antibiotic saline was applied after neuroendoscopic surgery (NES). Secondary hydrocephalus was treated by endoscopic third ventriculostomy or a ventriculoperitoneal shunt. Neuroendoscopic findings of CVI were used to classify patients into Grade Ⅰ(n = 3), Grade Ⅱ(n = 13), Grade Ⅲ(n = 10), and Grade Ⅳ(n = 6) CVI. The three patients with grade ⅠCVI underwent one NES, the 23 patients with grade Ⅱ/Ⅲ CVI underwent two NESs, and patients with grade Ⅳ CVI underwent two (n = 3) or three (n = 3) NESs. The imaging features and grades of neuroendoscopy results were positively related to the number of neurosurgical endoscopic procedures. Two patients died of multiple organ failure and the other 30 patients fully recovered. Among the 26 patients with secondary hydrocephalus, 18 received ventriculoperitoneal shunt and 8 underwent endoscopic third ventriculostomy. There were no recurrences of CVI during the 6- to 76-month follow-up after NES. Application of NESTs is an innovative method to assess and treat CVI, and its neuroendoscopic classification provides an objective, comprehensive assessment of CVI. The study trial was approved by the Institutional Review Board of Beijing Shijitan Hospital, Capital Medical University, China.

Improving mechanical properties of AZ91D magnesium/A356 aluminum bimetal prepared by compound casting via a high velocity oxygen fuel sprayed Ni coating

In this paper,a Ni coating was deposited on the surface of the A356 aluminum alloy by high velocity oxygen fuel spraying to improve the performance of the AZ91D magnesium/A356 aluminum bimetal prepared by a compound casting.The effects of the Ni coating as well as its thickness on microstructure and mechanical properties of the AZ91D/A356 bimetal were systematically researched for the first time.Results demonstrated that the Ni coating and its thickness had a significant effect on the interfacial phase compositions and mechanical properties of the AZ91D/A356 bimetal.The 10μm’s Ni coating cannot prevent the generation of the Al-Mg intermetallic compounds(IMCs)at the interface zone of the AZ91D/A356 bimetal,while the Ni coating with the thickness of 45μm and 190μm can avoid the formation of the Al-Mg IMCs.When the Ni coating was 45μm,the Ni coating disappeared and transformed into Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles at the interface zone.With a thickness of 190μm’s Ni coating,part of the Ni coating remained and the interface layer was composed of the Mg-Mg_(2)Ni eutectic structures+Ni_(2)Mg_(3)Al particles,Mg_(2)Ni layer,Ni solid solution(SS)layer,Al_(3)Ni_(2) layer,Al_(3)Ni layer and sporadic Al_(3)Ni+Al-Al_(3)Ni eutectic structures from AZ91D side to A356 side in sequence.The interface layer consisting of the Mg-Ni and Al-Ni IMCs obtained with the Ni coating had an obvious lower hardness than the Al-Mg IMCs.The shear strength of the AZ91D/A356 bimetal with a Ni coating of 45μm thickness enhanced 41.4%in comparison with that of the bimetal without Ni coating,and the fracture of the bimetal with 45μm’s Ni coating occurred between the Mg matrix and the interface layer with a mixture of brittle fracture and ductile fracture.

Effect of vibration on interfacial microstructure and mechanical properties of Mg/Al bimetal prepared by a novel compound casting

In this work,a vibration was applied in the preparation of the Mg/Al bimetal by a novel compound casting in order to improve the mechanical properties of the Mg/Al bimetal,and the effect of the vibration on the interfacial microstructure and mechanical properties of the Mg/Al bimetal was investigated.The results indicated that the vibration had a significant effect on the interfacial microstructure and mechanical properties of the Mg/Al bimetal,but it did not change the phase compositions of the interface,which was composed of layerⅠ(Al3Mg2+Mg2Si),layerⅡ(Al_(12)Mg_(17)+Mg_(2)Si)and layerⅢ(Al_(12)Mg_(17)/δ-Mg).Without vibration,the Mg_(2)Si phase with a needle-like morphology mainly aggregated in the layerⅡof the interface.After the application of the vibration,the SEM and EBSD analysis results showed that the Mg_(2)Si and Al3Mg2phases in the interface were obviously refined,and the distribution of the Mg_(2)Si became more uniform,due to the strong forced convection of the molten metal resulting from the vibration.The TEM analysis indicated that the interface between the A_(l3)Mg_(2) and Mg_(2)Si phases was non-coherent,suggesting the Mg_(2)Si particles cannot act as a heterogeneous nucleation base during the solidification process of the interface.Compared to the Mg/Al bimetal without vibration,the shear strength of the Mg/Al bimetal with vibration increased by about 50%from 31.7 MPa on average to 47.5 MPa,and the hardness of the layer I of the interface increased,and the hardness of the layerⅢdecreased.The fracture surface transformed from a flat fracture morphology without vibration to an irregular zigzag fracture morphology.

Evaluating Influential Factors on the Duration of Vehicle Fire Incidents Using Grey Relational Analysis

The duration of vehicle fire incidents has been closely associated with incidents loss. Understanding the influential priority of factors is significant to take targeted countermeasures for the managements. Based on the database from WSDOT （Washington Department of Transportation） in USA, we analyze the probability distribution of the vehicle fire accidents＇ duration. Then we classify the influential factors into the first-grade factors including three categories： time, incident type, operation and the second-grade factors including eight categories： quarter, week and day time, etc. Then GILA （grey relational analysis） model is applied to calculate grey relational grades of the influential factors. The results show that the most important factor of the first-grade factors is incident type, vehicles involved and agencies involved are the major factors among the second-grade factors.

Fabrication of Bio-inspired Superamphiphobic Aluminum Alloy Surface with Oil-triggered Wenzel-Slippery Transition via Femtosecond Laser

Surface-tension-confined microfluidic devices are platforms for manipulating 2D droplets based on patterned surfaces with special wettability.They have great potential for various applications,but are still in the early stages of development and face some challenges that need to be addressed.This study,inspired by the Wenzel and slippery transition of rose petal,develops a Patterned Oil-triggered Wenzel-slippery Surface(POWS)to examine the microfluidic devices.A laser-chemical composite method is established to fabricate POWSs,which take rose-petal-like microstructures as wettability pattern and a superamphiphobic surface as the background.The prepared POWSs switched between high adhesion superhydrophobic state and the slippery liquid-infused surface state through adding or removing the lubricant oil.In the high adhesion superhydrophobic state,the droplets can be sticked on the surface.In the slippery liquid-infused state,the droplet can slide along the wettability pattern as the designed route.A POWS-based droplet reactor is further constructed,on which,the droplets can be remotely controlled to move,mix and react,as required.Such a POWS,which manipulates droplets with surface tension controlled by the switchable wettability patterns,would be a promising candidate to construct multiple surface-tension-confined microfluidic devices.In addition,the fabrication technique and design principle proposed here may aid the development of various field related to the bio-inspired surfaces,such as water collection,desalination and high throughput analysis,etc.

供给侧改革背景下IPO抑价率的度量与解读

通过梳理中国询价机制实施以来的新股发行市场化改革重要事件,将中国新股发行市场化改革分为三个阶段。在第三阶段,证监会加快了新股发行的节奏,证交所限定了新股上市首日的涨跌幅,以首日涨跌幅为基础计算IPO抑价率的指标就无法体现该阶段个股间IPO抑价水平的差异。基于此提出了供给侧改革背景下IPO抑价率计算的新方法,同时从政策信号效应、投资者预期、改革时机选择等角度对该阶段IPO抑价新特征进行了解读,提出了中国新股发行市场化应坚持减少行政干预、加强顶层设计、加强信息披露监管、加强投资者教育的改革思路。

Efficacy analysis of flexible neuroendoscopy combined with dry-field techniques in the treatment of chronic subdural hematoma

Chronic subdural hematoma (CSDH) is a common and frequently occurring disease in neurosurgery, whose incidence accounts for around 10% of all intracranial hematomas. There have been many theories about the mechanism of CSDH, including acute subdural hematoma, slow hemorrhage after bridge vein injury, and traumatic subdural effusion evolution With improvements in medical imaging technology and related basic research, the perception of CSDH as an inflammatory vascular proliferative disease has gradually reached consensus In addition to head trauma, brain atrophy leading to expanded subdural space is the premise and primary reason for the occurrence of CSDH in the older adult population.