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Hierarchical Media Ethics in the Digital Age: An Analysis of the “Primary School Student Lost Homework in Paris” Incident
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作者 ZHAO Yifei 《Journalism and Mass Communication》 2024年第3期205-208,共4页
In the digital age,traditional media ethics norms lack sufficient explanatory power and binding force in practice.This paper uses the“Primary School Student Lost Homework in Paris”incident as a case study to explore... In the digital age,traditional media ethics norms lack sufficient explanatory power and binding force in practice.This paper uses the“Primary School Student Lost Homework in Paris”incident as a case study to explore the ethical controversies surrounding the dissemination of this event.By adopting a hierarchical media ethics perspective,the paper dynamically examines the ethical conduct of various communicators,elucidates the ethical responsibilities of each party involved,and reveals the complexity of communication ethics in the digital age. 展开更多
关键词 media ethics information dissemination self-media ethics norms “Primary School Student lost Homework in Paris”
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Effects of mechanical vibration on filling and solidification behavior, microstructure and performance of Al/Mg bimetal by lost foam compound casting 被引量:2
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作者 Guang-yu Li Feng Guan +3 位作者 Wen-ming Jiang Yuan-cai Xu Zheng Zhang Zi-tian Fan 《China Foundry》 SCIE EI CAS CSCD 2023年第6期469-479,共11页
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.... 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. 展开更多
关键词 lost foam casting filling and solidification processes Al/Mg bimetal mechanical vibration MICROSTRUCTURE mechanical properties
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Analysis of the Lost Circulation Problem
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作者 Xingquan Zhang Renjun Xie +2 位作者 Kuan Liu Yating Li Yuqiang Xu 《Fluid Dynamics & Materials Processing》 EI 2023年第6期1721-1733,共13页
The well-known“lost circulation”problem refers to the uncontrolled flow of whole mud into a formation.In order to address the problem related to the paucity of available data,in the present study,a model is introduc... The well-known“lost circulation”problem refers to the uncontrolled flow of whole mud into a formation.In order to address the problem related to the paucity of available data,in the present study,a model is introduced for the lost-circulation risk sample profile of a drilled well.The model is built taking into account effective data(the Block L).Then,using a three-dimensional geological modeling software,relying on the variation function and sequential Gaussian simulation method,a three-dimensional block lost-circulation risk model is introduced able to provide relevant information for regional analyses. 展开更多
关键词 GEOSTATISTICS risk assessment variation function sequential gaussian simulation drilling risk lost circulation evaluation method
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Estimating the Monetary Value of Hours Lost to the Nigerian Public Healthcare System When Full-Time Government Employee Doctors Engage in Dual Practice
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作者 Bartholomew S. Eze Mari Jones Imani Silver Kyaruzi 《Health》 CAS 2023年第2期215-238,共24页
Background: Dual Practice (DP) allows full-time public sector doctors to concurrently offer the same clinical services in the private sector. The debate against this practice seems to be largely influenced by its pote... Background: Dual Practice (DP) allows full-time public sector doctors to concurrently offer the same clinical services in the private sector. The debate against this practice seems to be largely influenced by its potential to reduce the contracted hours in the public sector and shift attention to private work. Purpose: The purpose of this secondary research is to estimate the monetary value of hours lost to the Nigerian public healthcare system when full-time government employee doctors are engaged in private practice. It attempts to quantify the amount of resource outflow from the public system due to absences and lateness arising from competition for time between the public system’s contracted hours and private practice. Methods: Sensitivity analysis in Excel 2010 was used to calculate doctors’ hourly pay in the public sector using the 2015 Consolidated Medical Salary Structure for medical and dental officers in Nigeria’s federal public service. The parameters used for the calculation were the official 40-hour working week and the average monthly gross pay of doctors on different grade levels. Hypothetical scenarios of hours lost due to absences associated with DP were created. The value of different hypothetical hour losses by the percentage of doctors assumed to engage in dual practice across all doctor grade levels was then computed. Results: The estimated annual value of hours lost from dual practice to a single public tertiary care hospital was N4,851,754 or 15,855 USD (best case scenario) and N19,407,017 or 63,422 USD (worst case scenario) for the normal routine work and N1,800,133 or 5883 USD (best case scenario) and N3,600,266 or 11,766 USD (worst case scenario) for the on-call duty. Conclusion: The government may have been paying salaries for large volumes of work not rendered in the public sector. The overall financial impact of dual practice in the Nigerian public system might be negative. 展开更多
关键词 Dual Practice Hours lost Nigeria Private Practice Public Healthcare Absences
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Oriental Utopia under the Gaze of the Other-A Brief Analysis of the Construction of the Oriental Image in Lost Horizon
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作者 ZHU Shuang-jie 《Journal of Literature and Art Studies》 2023年第5期340-346,共7页
Lost Horizon tells a story about Shangri-La,a paradise in the Orient.Throughout the construction of the Oriental image in the novel,it can be found that under its representation of being enslaved,driven,marginalized a... Lost Horizon tells a story about Shangri-La,a paradise in the Orient.Throughout the construction of the Oriental image in the novel,it can be found that under its representation of being enslaved,driven,marginalized and silenced,it implies a three-dimensional flow mechanism with multiple power-relationships interwoven between Orient and Occident,insiders and outsiders,“civilized”and“uncivilized”,male and female,etc.Driven by this mechanism,the Oriental image is integrated under a single abstract label,which has become a way for the Occident to re-understand,reconstruct and express itself after the war. 展开更多
关键词 lost Horizon “the Other” ORIENTALISM oriental image
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Microstructure and mechanical properties of Mg-Gd-Y-Zr alloy cast by metal mould and lost foam casting 被引量:15
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作者 李吉林 陈荣石 柯伟 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第4期761-766,共6页
The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr (mass fraction, %) alloy (GW104 alloy) cast by metal mould casting (MMC) and lost foam casting (LFC) were evaluated, respectively. It is r... The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr (mass fraction, %) alloy (GW104 alloy) cast by metal mould casting (MMC) and lost foam casting (LFC) were evaluated, respectively. It is revealed that different forming modes do not influence the phase composition of as-cast alloy. In the as-cast specimens, the microstructures are similar and composed of α-Mg solid solution, eutectic compound of α-Mg+Mg 24 (Gd, Y) 5 and cuboid-shaped Mg 5 (Gd, Y) phase; whereas the average grain size of the alloy produced by metal mould casting is smaller than that by lost foam casting. The eutectic compound of the alloy is completely dissolved after solution treatment at 525 ℃for 6 h, while the Mg 5 (Gd, Y) phase still exists after solution treatment. After peak-ageing, the lost foam cast alloy exhibits the maximum ultimate tensile strength of 285 MPa, and metal mould cast specimen 325 MPa at room temperature, while the tensile yield strengths of them are comparable. It can be concluded that GW104 alloy cast by lost foam casting possesses similar microstructure and evidently lower mechanical strength compared with metal mould cast alloy, due to slow solidification rate and proneness to form shrinkage porosities during lost foam casting process. 展开更多
关键词 Mg-Gd-Y-Zr alloy lost foam casting metal mould casting MICROSTRUCTURE mechanical property
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Lost City低温热液场——一种新的海底热液活动类型 被引量:6
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作者 钱江初 于刚 +2 位作者 刘春秋 雷吉江 初凤友 《海洋学研究》 北大核心 2006年第1期43-49,共7页
综述了新近发现的海底热液活动的新类型——Lost City低温热液场。该低温热液场坐落于距洋中脊15km远的轴外洋底上,下伏的橄榄石经蛇纹石化反应所产生的热能是驱动该热液场的热源。低温热液场烟囱结构的矿物组分主要为方解石、文石和... 综述了新近发现的海底热液活动的新类型——Lost City低温热液场。该低温热液场坐落于距洋中脊15km远的轴外洋底上,下伏的橄榄石经蛇纹石化反应所产生的热能是驱动该热液场的热源。低温热液场烟囱结构的矿物组分主要为方解石、文石和水镁石,热液流的温度为40~75℃.并以高pH值以及高氢、高甲烷含量为特征。Lost City低温热液场,为研究者们了解早期地球热液过程与它们所支撑的生命系统关系,探讨蛇纹石化、碳酸盐沉淀、微生物活动之间关系提供了天然实验室。 展开更多
关键词 热液硫化物 lost City低温热液场 低温热液作用 蛇纹石化反应
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Machine learning for carbonate formation drilling: Mud loss prediction using seismic attributes and mud loss records
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作者 Hui-Wen Pang Han-Qing Wang +4 位作者 Yi-Tian Xiao Yan Jin Yun-Hu Lu Yong-Dong Fan Zhen Nie 《Petroleum Science》 SCIE EI CAS CSCD 2024年第2期1241-1256,共16页
Due to the complexity and variability of carbonate formation leakage zones, lost circulation prediction and control is one of the major challenges of carbonate drilling. It raises well-control risks and production exp... Due to the complexity and variability of carbonate formation leakage zones, lost circulation prediction and control is one of the major challenges of carbonate drilling. It raises well-control risks and production expenses. This research utilizes the H oilfield as an example, employs seismic features to analyze mud loss prediction, and produces a complete set of pre-drilling mud loss prediction solutions. Firstly, 16seismic attributes are calculated based on the post-stack seismic data, and the mud loss rate per unit footage is specified. The sample set is constructed by extracting each attribute from the seismic trace surrounding 15 typical wells, with a ratio of 8:2 between the training set and the test set. With the calibration results for mud loss rate per unit footage, the nonlinear mapping relationship between seismic attributes and mud loss rate per unit size is established using the mixed density network model.Then, the influence of the number of sub-Gausses and the uncertainty coefficient on the model's prediction is evaluated. Finally, the model is used in conjunction with downhole drilling conditions to assess the risk of mud loss in various layers and along the wellbore trajectory. The study demonstrates that the mean relative errors of the model for training data and test data are 6.9% and 7.5%, respectively, and that R2is 90% and 88%, respectively, for training data and test data. The accuracy and efficacy of mud loss prediction may be greatly enhanced by combining 16 seismic attributes with the mud loss rate per unit footage and applying machine learning methods. The mud loss prediction model based on the MDN model can not only predict the mud loss rate but also objectively evaluate the prediction based on the quality of the data and the model. 展开更多
关键词 lost circulation Risk prediction Machine learning Seismic attributes Mud loss records
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Research progress and development of deep and ultra-deep drilling fluid technology
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作者 SUN Jinsheng YANG Jingbin +2 位作者 BAI Yingrui LYU Kaihe LIU Fengbao 《Petroleum Exploration and Development》 SCIE 2024年第4期1022-1034,共13页
The research progress of deep and ultra-deep drilling fluid technology systematically reviewed,the key problems existing are analyzed,and the future development direction is proposed.In view of the high temperature,hi... The research progress of deep and ultra-deep drilling fluid technology systematically reviewed,the key problems existing are analyzed,and the future development direction is proposed.In view of the high temperature,high pressure and high stress,fracture development,wellbore instability,drilling fluid lost circulation and other problems faced in the process of deep and ultra-deep complex oil and gas drilling,scholars have developed deep and ultra-deep high-temperature and high-salt resistant water-based drilling fluid technology,high-temperature resistant oil-based/synthetic drilling fluid technology,drilling fluid technology for reservoir protection and drilling fluid lost circulation control technology.However,there are still some key problems such as insufficient resistance to high temperature,high pressure and high stress,wellbore instability and serious lost circulation.Therefore,the development direction of deep and ultra-deep drilling fluid technology in the future is proposed:(1)The technology of high-temperature and high-salt resistant water-based drilling fluid should focus on improving high temperature stability,improving rheological properties,strengthening filtration control and improving compatibility with formation.(2)The technology of oil-based/synthetic drilling fluid resistant to high temperature should further study in the aspects of easily degradable environmental protection additives with low toxicity such as high temperature stabilizer,rheological regulator and related supporting technologies.(3)The drilling fluid technology for reservoir protection should be devoted to the development of new high-performance additives and materials,and further improve the real-time monitoring technology by introducing advanced sensor networks and artificial intelligence algorithms.(4)The lost circulation control of drilling fluid should pay more attention to the integration and application of intelligent technology,the research and application of high-performance plugging materials,the exploration of diversified plugging techniques and methods,and the improvement of environmental protection and production safety awareness. 展开更多
关键词 deep and ultra-deep drilling high temperature resistant drilling fluid reservoir protection drilling fluid lost circulation control safety and environmental protection technical prospects
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Clinical efficacy and safety of kyphoplasty for the treatment of osteoporotic vertebral compression fractures at different surgical timings based on the theory of“dynamic-static integration”
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作者 Zunwang Li Jiang Chen +3 位作者 Dekui Li Jiayu Yang Jiaqi Qin Yuqing Guan 《Journal of Traditional Chinese Medical Sciences》 CAS 2024年第1期86-92,共7页
Objective:To investigate the clinical efficacy and safety of percutaneous kyphoplasty at different surgical timings in the treatment of osteoporotic vertebral compression fracture(OVCF)based on the theory of“dynamic-... Objective:To investigate the clinical efficacy and safety of percutaneous kyphoplasty at different surgical timings in the treatment of osteoporotic vertebral compression fracture(OVCF)based on the theory of“dynamic-static integration”.Methods:Patients with OVCF who underwent percutaneous kyphoplasty in our hospital were selected and divided into Groups A,B,and C for those undergoing surgery within 7,7—21,and>21 days of fracture occurrence.The variations in the amount of bone cement injected,pre-and post-operative pain levels,functional activity,deformity correction of the injured vertebrae,bone cement leakage,and vertebral body height loss were compared among the three groups.Results:Regarding pain relief and functional activity,the postoperative Visual Analog Scale and Oswestry Disability Index scores of the three groups significantly improved.Furthermore,the deformities of the injured vertebrae in the three groups were significantly corrected,with Groups A and B exhibiting superior correction compared to Group C.Moreover,the bone cement leakage rates in groups A and C were higher than that in Group B.At the 3-month follow-up,the loss of vertebral height in Group C was significantly higher than those in groups A and B.Conclusion:Kyphoplasty is effective for OVCF treatment.Early surgery can effectively restore the vertebral height of the injured vertebra,reduce kyphosis,and reduce height loss of the injured vertebra after surgery;nevertheless,treatment within 1—3 weeks of the fracture can reduce the occurrence of bone cement leakage,making the surgery safer.Therefore,surgical treatment within 1—3 weeks of fracture is safer and can achieve satisfactory therapeutic effects.From the perspective of traditional Chinese medicine,PKP surgery can transform the fracture end from a micromotion state to a fixed state,which fully embodies the theory of“dynamic-static integration”. 展开更多
关键词 KYPHOPLASTY Operation timing Bone cement leakage lost height of injured vertebra
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Can the Hypothetical Protons Emitted by the Shroud’s Man Furnish an I(z) Correlation?
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作者 Giovanni Fazio 《Open Journal of Applied Sciences》 2024年第8期1979-1984,共6页
Recently, we have investigated the hypothesis radiative demonstrating that the two penetrated thicknesses (in air and linen) are not compatible with a single energy of the protons. Furthermore, we deduced that the dis... Recently, we have investigated the hypothesis radiative demonstrating that the two penetrated thicknesses (in air and linen) are not compatible with a single energy of the protons. Furthermore, we deduced that the distribution of energy, released by the above particles, on the burial linen has not a linear trend when the body-burial linen distance changes. Now, in this article we want to deduce the I(z) relationship, between the Image Intensity of the colour produced by protons on a linen and the z distance from the source (of Protons) and the same linen. To achieve the result in an analytical form and make a comparison with the same function extracted from the Shroud, we used the empirical expression Range-Energy for protons in air of Wilson-Brobeck. Thus, we obtain a result I(z) = Im [1 − (z/R)5/9] that is different from the one extracted from the Turin Linen I(z) = IM (1 − z/R0). We have also the same information using the Range-Energy curves for protons of Rogozinski. The result is negative for the radiative hypothesis that is unable to produce the Shroud Body Image. Therefore, to investigate the above unknown process of formation, it is necessary to think about another one. 展开更多
关键词 Hypothesis Radiative Protons in the Matter Energy lost by Protons I(z) Correlations Comparison
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COCA语料库在教学中的应用——以lost in thoughts为例
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作者 兰丽珍 《湖北广播电视大学学报》 2014年第1期147-148,共2页
文章通过在线COCA语料库探讨了lost in thoughts的应用。阐明在传统的字典中没列入的短语不表示不存在,在我们学习,教学,研究应该充分利用语料库打破传统的一些误区,更好地了解本族语者的使用语境。
关键词 COCA语料库 lost in THOUGHTS lost in THOUGHT
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《The Lost Garden》的文体学分析
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作者 蔡秋文 《宿州学院学报》 2013年第6期52-55,共4页
《The Lost Garden》是美国著名华裔儿童文学作家叶祥添的自传,已被选录入美国中学世界文学教科书,从文体学的角度入手,对《The Lost Garden》的语言特征进行研析,能更深入地挖掘美籍华裔作家叶祥添的语言风格、语用意图和创作主旨。运... 《The Lost Garden》是美国著名华裔儿童文学作家叶祥添的自传,已被选录入美国中学世界文学教科书,从文体学的角度入手,对《The Lost Garden》的语言特征进行研析,能更深入地挖掘美籍华裔作家叶祥添的语言风格、语用意图和创作主旨。运用文体学方法,从词汇、句子、语篇及修辞等四个不同的层面,对《The Lost Garden》的文体特征进行细致分析,通过探讨该文本语言在这四个不同层面的特征,作品的语言特色得以凸现,读者得以更走近文本,这有助于读者更深刻地理解该文本的文体风格,更准确地分析作品的人物特征及把握作者的意图,从而更加全面、正确地理解和鉴赏作品。 展开更多
关键词 叶祥添 《The lost Garden》 文体学分析
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The Lost Generation and its significance to American Culture
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作者 尹剑波 刘佳 《科教文汇》 2007年第17期189-,193,共2页
The Lost Generation is actually a group of American writers who were rebelling against what America had become by the 1900s.The Lost generation tendency and Lost generation writers are of great importance to the Ameri... The Lost Generation is actually a group of American writers who were rebelling against what America had become by the 1900s.The Lost generation tendency and Lost generation writers are of great importance to the American and world literature.This article serves as a brief introduction to the Lost generation and its significant writers. 展开更多
关键词 The lost GENERATION COSMOPOLITAN SIGNIFICANCE LITERATURE
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皮拉尼西 Lost in Beijing
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作者 傅刚 《北京规划建设》 2005年第6期164-167,共4页
关键词 lost 物质生活 in 现代化
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Research progress and prospect of plugging technologies for fractured formation with severe lost circulation 被引量:8
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作者 SUN Jinsheng BAI Yingrui +6 位作者 CHENG Rongchao LYU Kaihe LIU Fan FENG Jie LEI Shaofei ZHANG Jie HAO Huijun 《Petroleum Exploration and Development》 CSCD 2021年第3期732-743,共12页
By reviewing the mechanisms of drilling fluid lost circulation and its control in fractured formations, the applicability and working mechanisms of different kinds of lost circulation materials in plugging fractured f... By reviewing the mechanisms of drilling fluid lost circulation and its control in fractured formations, the applicability and working mechanisms of different kinds of lost circulation materials in plugging fractured formations have been summarized. Meanwhile, based on the types of lost circulation materials, the advantages, disadvantages, and application effects of corresponding plugging technologies have been analyzed to sort out the key problems existing in the current lost circulation control technologies. On this basis, the development direction of plugging technology for severe loss have been pointed out. It is suggested that that the lost circulation control technology should combine different disciplines such as geology, engineering and materials to realize integration, intelligence and systematization in the future. Five research aspects should be focused on:(1) the study on mechanisms of drilling fluid lost circulation and its control to provide basis for scientific selection of lost circulation material formulas, control methods and processes;(2) the research and development of self-adaptive lost circulation materials to improve the matching relationship between lost control materials and fracture scales;(3) the research and development of lost circulation materials with strong retention and strong filling in three-dimensional fracture space, to enhance the retention and filling capacities of materials in fractures and improve the lost circulation control effect;(4) the research and development of lost circulation materials with high temperature tolerance, to ensure the long-term plugging effect of deep high-temperature formations;(5) the study on digital and intelligent lost circulation control technology, to promote the development of lost circulation control technology to digital and intelligent direction. 展开更多
关键词 severe lost circulation lost circulation control mechanism lost circulation materials lost circulation control technology drilling fluid lost circulation plugging technologies progress
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High Cr white cast iron/carbon steel bimetal liner by lost foam casting with liquid-liquid composite process 被引量:10
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作者 Xiao Xiaofeng Ye Shengping +2 位作者 YinWeixin Zhou Xiaoguang Xue Qiong 《China Foundry》 SCIE CAS 2012年第2期136-142,共7页
Liners in wet ball mill for mineral processing industry must bear abrasive wear and corrosive wear, and consequently, the service life of the liner made from traditional materials, such as Hadfield steel and alloyed s... Liners in wet ball mill for mineral processing industry must bear abrasive wear and corrosive wear, and consequently, the service life of the liner made from traditional materials, such as Hadfield steel and alloyed steels, is typically less than ten months. Bimetal liner, made from high Cr white cast iron and carbon steel, has been successfully developed by using liquid-liquid composite lost foam casting process. The microstructure and interface of the composite were analyzed using optical microscope, SEM, EDX and XRD. Micrographs indicate that the boundary of bimetal combination regions is staggered like dogtooth, two liquid metals are not mixed, and the interface presents excellent metallurgical bonding state. After heat treatment, the composite liner specimens have shown excellent properties, including hardness 〉 61 HRC, fracture toughness ak 〉16.5 J.cm2 and bending strength 〉1,600 MPa. Wear comparison was made between the bimetal composite liner and alloyed steel liner in an industrial hematite ball mill of WISCO, and the results of eight-month test in wet grinding environment have proved that the service life of the bimetal composite liner is three times as long as that of the alloyed steel liner. 展开更多
关键词 bimetal liner liquid-liquid composite process lost foam casting high Cr white cast iron
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Influence of mechanical vibration on the solidification of a lost foam cast 356 alloy 被引量:7
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作者 Zhao Zhong Fan Zitian +3 位作者 Dong Xuanpu Tang Bo Pan Di Li Jiqiang 《China Foundry》 SCIE CAS 2010年第1期24-29,共6页
Mechanical vibration was applied to the solidification of a lost foam cast(LFC) 356 aluminum alloy.Effects of mechanical vibration,with different peak acceleration,on the size and morphology of α-Al phase,and also on... Mechanical vibration was applied to the solidification of a lost foam cast(LFC) 356 aluminum alloy.Effects of mechanical vibration,with different peak acceleration,on the size and morphology of α-Al phase,and also on the mechanical properties of the castings were studied.Results indicated that α-Al dendrites gradually grow into equiaxed grains as the peak acceleration of vibration is increased.When the peak acceleration is between about 1 to 4 g,α-Al phase distribution is uniform and is refined obviously.α-Al dendrites are reduced and the mechanical properties of the castings are improved significantly when compared to those of the castings that are produced without vibration.However,when the peak acceleration is higher than 4 g,strong vibration will lead to defects formation,such as sand adhesion,while the amount and size of pores will be increased.And due to the turbulent flow that caused by strong vibration,the chance of forming large pores in the matrix has been increased significantly.The increase in defects will result in the deterioration of mechanical properties. 展开更多
关键词 aluminum alloy microstructure mechanical property lost foam casting mechanical vibration
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Effect of Process Parameters on Porosity in Aluminum Lost Foam Process 被引量:7
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作者 Kiyoung KIM Kyongwhoan LEE 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2005年第5期681-685,共5页
Porosity is a main defect in aluminum alloy castings, which is also thought to be severe in aluminum alloy castings produced by lost foam process due to the pyrolysis of the polystyrene foam pattern during pouring. Fu... Porosity is a main defect in aluminum alloy castings, which is also thought to be severe in aluminum alloy castings produced by lost foam process due to the pyrolysis of the polystyrene foam pattern during pouring. Fundamental experiments were carried out to evaluate the effect of process parameters such as the melt treatment, the cooling rate and the density of expanded polystyrene (EPS) foam on porosity in A356.2 bar casting. The effect of melt treatment including degassing and refining was investigated. The effect of cooling rate was also evaluated by changing the mold packing material such as the silica sand, the zircon sand and the steel shots. Gas entrapment due to the turbulent metal flow during mold filling in conventional molding process results in porosity. Mold filling sequence in lost foam process is different from that in conventional molding process. The effect of molten metal flow was estimated by comparing the density of the casting by conventional sodium silicate molding with that by lost foam process. Density measurement was conducted to analyze the extent of porosity in the casting. Source of the porosity in lost foam process can be divided into two factors, i.e. turbulence in molten metal flow and entraining residue or gas from the pattern during pouring. 展开更多
关键词 lost foam process Mold packing material EPS foam POROSITY Melt treatment
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Status quo and development trend of lost foam casting technology 被引量:7
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作者 Fan Zitian Jiang Wenming +1 位作者 Liu Fuchu Xiao Botao 《China Foundry》 SCIE CAS 2014年第4期296-307,共12页
Lost foam casting(LFC)technology has been widely applied to cast iron and cast steel.However,the development of LFC for Al and Mg alloys was relatively slower than that for cast iron and cast steel.The application of ... Lost foam casting(LFC)technology has been widely applied to cast iron and cast steel.However,the development of LFC for Al and Mg alloys was relatively slower than that for cast iron and cast steel.The application of LFC to Al and Mg alloys needs more effort,especially in China.In this paper,the development history of LFC is reviewed,and the application situations of LFC to Al and Mg alloys are mainly discussed.Meanwhile,the key problems of LFC for Al and Mg alloys are also pointed out.Finally,the prospects for LFC technology are discussed,and some special new LFC technologies are introduced for casting Al and Mg alloys.In future,the development trends of green LFC technology mainly focus on the special new LFC methods,metal material,coating,heat treatment,new foam materials as well as purification technology of tail gas,etc. 展开更多
关键词 lost foam casting(LFC) technology actuality development trend aluminum alloy magnesium alloy
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