Influence of introducing Zr,Ti,Nb and Ce elements on externally solidified crystals and mechanical properties of high-pressure die-casting Al–Si alloy

High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress arouses the deformation of large integrated die-castings.Herein,the development of non-heat treatment Al alloys is becoming the hot topic.In addition,HPDC contains externally solidified crystals(ESCs),which are detrimental to the mechanical properties of castings.To achieve high strength and toughness of non-heat treatment die-casting Al-Si alloy,we used AlSi9Mn alloy as matrix with the introduction of Zr,Ti,Nb,and Ce.Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation.Our results reveal that the addition of Ti increased ESCs'size and porosity,while the introduction of Nb refined ESCs and decreased porosity.Meanwhile,large-sized Al_3(Zr,Ti)phases formed and degraded the mechanical properties.Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.

INSURE技术联合T-piece治疗新生儿呼吸窘迫综合征的临床有效性

目的探讨新生儿呼吸窘迫综合征(respiratory distress syndrome,RDS)采用INSURE技术+Tpiece方法完成治疗的有效性。方法回顾性选取2023年1—12月齐齐哈尔医学院附属第二医院收治的50例RDS患儿的临床资料,根据不同的治疗方法分为对照组(25例,复苏囊+INSURE技术)、研究组(25例,INSURE技术+T-piece方法)。比较两组血氧饱和度最低值、平均吸氧浓度、鼻塞持续气道正压通气应用时间、心率、并发症发生率。结果研究组血氧饱和度最低值为(90.79±3.59)%,高于对照组的(81.33±2.85)%,差异有统计学意义(t=10.319,P<0.05)。研究组平均吸氧浓度、鼻塞持续气道正压通气应用时间、心率优于对照组,差异有统计学意义(P均<0.05)。两组并发症总发生率比较,差异无统计学意义(P>0.05)。结论临床对RDS患儿在治疗期间,将INSURE技术以及T-piece方法进行充分结合,可有效改善患儿的氧合及血气指标,促进病情康复。

基于语料分析的文化负载词英译描述性研究——以Thousand Pieces of Gold为例

母语为英语的华裔作家多以海外华人生活或华人历史为背景进行文学创作,他们的文学创作呈现出一种用英语表达中国社会文化的‘翻译性',是一种涉及到英语母语和目的语汉语两种语言的转换的文学创作。鉴于这种特殊性,本研究以Ruthanne Lum McCunn的英文原版小说Thousand Pleces of Gold(《千金》)作为研究文本,结合语料对作品中汉语文化负载词的英语表达规律进行描述分析来探讨汉语文化负载词的英译策略。

Microstructure and mechanical properties of Mg-6Gd-3Y-0.5Zr alloy processed by high-vacuum die-casting

GW63K （Mg-6Gd-3Y-0.5Zr） magnesium alloys were prepared successfully by high-vacuum die-casting. Effects of fast shot speed and vacuum level on the grain size and mechanical properties of this alloy were studied. Microstructure of the alloys was analyzed by SEM, EDX and optical microscope （OM）. The effect of heat treatment on high vacuum die-casting （HVDC） GW63K alloy was also studied. The results indicate that with the increase of fast velocity, the tensile yield strength hardly changes, but the elongation first increases, then decreases. The optimum heat treatment process is solution treatment at 748 K for 2 h and aging at 473 K for 80 h. Under this condition, GW63K magnesium alloy exhibits a maximum tensile strength and elongation of 308 MPa and 9.45%. There is significant correlation between ductility and the presence of external solidified cells （ESCs）. The as-cast GW63K alloy consists ofα-Mg and Mg24（Gd,Y）5 particles. After heat treatment, Gd and Y atoms dissolve intoα-Mg matrix.

针对BitTorrent协议中Piece消息的隐写分析方法

网络隐写是当前网络攻击中常见的一种隐蔽通信方式,给网络安全造成了极大隐患。BitTorrent网络作为一种使用极为广泛的协议,拥有巨大流量,是隐藏信息的极佳载体。近来,有研究者提出了一种基于Piece消息的网络隐写方法,公开文献中尚无有效的检测算法。针对此,提出一种基于多特征分类的检测方法。提取正常和含密Piece消息数据流;提取网络数据流时间序列的均值、方差与信息熵特征;使用SVM分类器给出检测结果。实验结果显示,在观测窗口为1000个数据包时,该方法对基于Piece消息隐写的检测率可达94.7%。

FPSO船体结构建造Piece Mark进度报表开发与应用

本文针对国外业主对Piece Mark表的提交需求,结合海洋石油工程股份有限公司的PCMS系统,采用VSTO编程技术,对该进度报表进行了研究和开发,并在某国外FPSO船体建造项目中进行了应用。

A review of magnesium die-castings for closure applications

Vehicle mass reduction in the automotive industry has become an industry-wide objective.Increasing fuel efficiency and greenhouse gas emission targets for engine-powered vehicles,and ambitions for extended range electric vehicles have motivated these reductions in vehicle mass.Mass reduction opportunities in structural automotive applications are increasingly realized through lightweight alloy castings,such as magnesium,primarily due to the ease of component substitution.The traditional benefits of magnesium die-castings including lightweighting and associated compounded mass savings,excellent strength-to-weight ratio,part consolidation,near net-shape forming,dimensional repeatability,and integration of additional components can be realized in closure applications.One recent example is the application of a magnesium die-casting for the structural inner of the liftgate in the 2017 Chrysler Pacifica,replacing nine parts in the previous generation and resulting in a liftgate assembly weight reduction of nearly 50%.The work presented here reviews past and current developments of magnesium die-castings in closure applications and discusses the benefits and challenges of magnesium alloys for these applications,including casting design,corrosion and fastening strategies,and the manufacturing design and assembly methodologies.

Development of vacuum die-casting process

The vacuum die-casting process,started 25 years ago in Japan,has been widely applied.This technology contributes very much to improvement of castings quality.The main factor causing the defects of die castings is the trapped air in the mold cavity,while the key technology of vacuum die-casting process is to avoid the trapped air effectively by evacuating the cavity before casting.At the same time,due to the shot speed and the casting pressure reduced in half,the service life of the die is prolonged and the productivity is enhanced,as well.Vacuum die-casting process is of great signif icance in improving the die castings quality and making up the shortcomings of super-high-speed shot casting.

Identification of Kinematic Errors of Five-axis Machine Tool Trunnion Axis from Finished Test Piece

Compared with the traditional non-cutting measurement,machining tests can more accurately reflect the kinematic errors of five-axis machine tools in the actual machining process for the users.However,measurement and calculation of the machining tests in the literature are quite difficult and time-consuming.A new method of the machining tests for the trunnion axis of five-axis machine tool is proposed.Firstly,a simple mathematical model of the cradle-type five-axis machine tool was established by optimizing the coordinate system settings based on robot kinematics.Then,the machining tests based on error-sensitive directions were proposed to identify the kinematic errors of the trunnion axis of cradle-type five-axis machine tool.By adopting the error-sensitive vectors in the matrix calculation,the functional relationship equations between the machining errors of the test piece in the error-sensitive directions and the kinematic errors of C-axis and A-axis of five-axis machine tool rotary table was established based on the model of the kinematic errors.According to our previous work,the kinematic errors of C-axis can be treated as the known quantities,and the kinematic errors of A-axis can be obtained from the equations.This method was tested in Mikron UCP600 vertical machining center.The machining errors in the error-sensitive directions can be obtained by CMM inspection from the finished test piece to identify the kinematic errors of five-axis machine tool trunnion axis.Experimental results demonstrated that the proposed method can reduce the complexity,cost,and the time consumed substantially,and has a wider applicability.This paper proposes a new method of the machining tests for the trunnion axis of five-axis machine tool.

Surface Magnet Gears with a New Magnet Arrangement and Optimal Shape of Stationary Pole Pieces

In mechanical gear systems, dust, noise, vibration, and tooth wear are generated by frictions among gear teeth, and suppressing friction requires lubrication. Magnetic gears transmit torque by magnetic forces without contact and so avoid contact-related problems. The present paper discusses magnet arrangements and the shape of stationary gear teeth to improve transmission torque in surface magnet type magnetic gear transmission mechanisms.

A Dual-Platform Laser Scanner for 3D Reconstruction of Dental Pieces

This paper presents a dual-platform scanner for dental reconstruction based on a three-dimensional(3D)laser-scanning method.The scanner combines translation and rotation platforms to perform a holistic scanning.A hybrid calibration method for laser scanning is proposed to improve convenience and precision.This method includes an integrative method for data collection and a hybrid algorithm for data processing.The integrative method conveniently collects a substantial number of calibrating points with a stepped gauge and a pattern for both the translation and rotation scans.The hybrid algorithm,which consists of a basic model and a compensation network,achieves strong stability with a small degree of errors.The experiments verified the hybrid calibration method and the scanner application for the measurement of dental pieces.Two typical dental pieces were measured,and the experimental results demonstrated the validity of the measurement that was performed using the dual-platform scanner.This method is effective for the 3D reconstruction of dental pieces,as well as that of objects with irregular shapes in engineering fields.

Simulation of α-Al grain formation in high vacuum die-casting Al-Si-Mg alloys with multi-component quantitative cellular automaton method

Al-Si-Mg alloys are the most commonly used material in high vacuum die-casting(HVDC),in which the morphology and distribution ofα-Al grains have important effect on mechanical properties.A multi-component quantitative cellular automaton(CA)model was developed to simulate the microstructure and microsegregation of HVDC Al-Si-Mg alloys with different Si contents(7%and 10%)and cooling rates during solidification.The grain number and average grain size with electron backscatter diffraction(EBSD)analysis were used to verify the simulation.The relationship between grain size and nucleation order as well as nuclei density was investigated and discussed.It is found that the growth of grains will be restrained in the location with higher nuclei density.The influence of composition and cooling rate on the solute transport reveals that for AlSi7Mg0.3 alloy the concentration of solute Mg in liquid is higher at the beginning of eutectic solidification.The comparison between simulation and experiment results shows that externally solidified crystals(ESCs)have a significant effect for samples with high cooling rate and narrow solidification interval.

Torsional vibration analysis of lathe spindle system with unbalanced workpiece

For the purpose of analyzing the torsional vibration caused by the gravitational unbalance torque arisen in a spindle system when it is machining heavy work piece,a 10-DOF lumped parameter model was made for the machine tool spindle system with geared transmission.By using the elementary method and Runge-Kutta method in Matlab,the eigenvalue problem was solved and the pure torsional vibration responses were obtained and examined.The results show that the spindle system cannot operate in the desired constant rotating speed as far as the gravitational unbalance torque is engaged,so it may cause bad effect on machining accuracy.And the torsional vibration increases infinitely near the resonant frequencies,so the spindle system cannot operate normally during these spindle speed ranges.

Thin-Wall Aluminum Die-Casting Technology for Development of Notebook Computer Housing

Silicon-based aluminum casting alloys are known to be one of the most widely used alloy systems mainly due to their superior casting characteristics and unique combination of mechanical and physical properties. However,manufacturing of thin-walled aluminum die-casting components,less than 1.0 mm in thickness,is generally known to be very difficult task to achieve aluminum casting alloys with high fluidity.Therefore,in this study,the optimal die-casting conditions for producing 297 mm×210 mm×0.7 mm thin-walled aluminum component was examined experimentally by using 2 different gating systems,tangential and split type,and vent design.Furthermore,computational solidification simulation was also conducted.The results showed that split type gating system was preferable gating design than tangential type gating system at the point of view of soundness of casting and distortion generated after solidification.It was also found that proper vent design was one of the most important factors for producing thin-wall casting components because it was important for the fulfillment of the thin-wall cavity and the minimization of the casting distortion.

Mold Filling and Prevention of Gas Entrapment in High-pressure Die-casting

This paper presents some results of direct observation of mold filling in a specially designed die-casting by X-ray diffraction, including comparison with numerical simulation. Based on such work the authors discuss how to prevent gas entrapment and propose new methods.

“a piece of+名词”与其修饰语

在“a piece of+名词”结构中,作修饰语的形容词出现在piece 之前与出现在名词之前这两种情况都有。例如: a piece of good luck;a piece of bad news 与 a finepiece of work;a delicate piece of mechanism 等等。还可以举出许多例子。那么,这是否就等于说该结构中的形容词可以任意放在上述两个位置中的一个上呢?也不尽然。笔者查阅了若干词典。

Finite element analysis of multi-piece post-crown restoration using different types of adhesives

The multi-piece post-crown technique is more effective in restoring residual root than other restoration techniques.Various types of adhesives have different material properties that affect restoration.Therefore,the choice of adhesive is particularly important for patients.However,the effect of different kinds of adhesives was not too precise by experimental methods when concerning about individual differences of teeth.One tooth root can only be restored with one type of adhesive in experiment.After the mechanical test,this tooth root cannot be restored with other adhesives.With the help of medical imaging technology,reverse engineering and finite element analysis,a molar model can be reconstructed precisely and restored using different types of adhesives.The same occlusal and chewing loads were exerted on the same restored residual root models with different types of adhesives separately.Results of von Mises stress analysis showed that the adhesives with low Young’s modulus can protect the root canal effectively.However,a root canal concentration is apparently produced around the root canal orifice when chewing.Adhesives with large Young’s modulus can buffer the stress concentration of the root canal orifice.However,the root canal tissue may be destroyed because the adhesive is too hard to buffer the load.

Opportunities and challenges of Chinese die-casting market

The present status and perspectives of Chinese die-casting market were commented. In 2003, the total output of die castings in the whole country was 708000 tons, in which the outputs of Al-alloy, Zn-alloy, Mg-alloy, Cu-alloy die castings were 474600 tons, 222000 tons, 5800 tons, 5600 tons, respectively, each accounted for 67%, 31.35%, 0.85%, 0.8% of the total. The annual sale volume of die-casting machines was approximately 1800. And the gross output value of dies approached RMB 38 billion, in which die-casting dies accounted for about 10%. In the die-casting industry of the entire country, the foreign capital enterprises, public-run enterprises, township and village enterprises, private enterprises accounted for over 80% of the total die-casting enterprises. Super huge die-casting groups are forming.

Development and Application of Die-Casting High Speed Steel Rolls

Due to its high hardness,good red hardness and excellent wear resistance at high temperature,high speed steel(HSS)is fit for the roll manufacture.In order to overcome the segregation of centrifugal casting of HSS roll,die-cast processes were developed and its effects on the properties of the HSS roll were investigated.It was found that pressure,pressing time and speed are three important factors affecting shrinkage cavity.For pouring temperature of 1 400-1 450 ℃,pressure of 150-160 MPa,pressing time of 120-150 sand pressing speed of 14-16mm/s,a compact HSS roll was obtained,which has no segregation and small working allowance.In the high speed wire rod rolling mill,service life of the HSS roll is 5to 8times longer than that of high nickel chromium infinite chilled cast iron roll.

Code generation and recognition using a modified ejection system in die-casting process

A code-generation and recognition technology that uses a modified ejection system in the diecasting process is presented.To achieve the highest level of quality management,the first requirement in the manufacturing process is to establish a product management system according to the specific product unit.Thus,a method to individually identify each product,such as a barcode or QR code,is required during the production process.Products manufactured in the die-casting process always have ejector pin(EP)marks.Herein,an ejection system was modified to generate a unique code using EP marks.This ejection system has two features:an EP with a modified head to show the direction of rotation,and a function to dependently rotate EPs(five or six EPs)with a constant angle.The EPs are numbered according to the rotation angle.Thus,the EP marks can be viewed as a five-or six-digit code.A program was also developed to individually identify the products by automatically detecting and reading the EPs using deep learning-based object detection and classification technology.