A new challenge: grain boundary engineering for advanced materials by magnetic field application

This paper gives an overview of “Grain boundary engineering (GBE) for advanced materials by magnetic field application” based on recent experimental work performed on different kinds of structural and functional materials. It is shown that magnetic field application has a great potential and unique advantage as “non-contact processing” for microstructure control, irreplaceable by any other existing processing methods. The control of grain growth and texture by magnetic fields has been found to be generally applicable to many metallic materials, irrespective of whether they are ferromagnetic or not. Grain growth which is controlled by grain boundary migration was found to be strongly affected by magnetic field application. Recent attempts at the grain boundary engineering by magnetic field application through phase transformation have revealed that magnetic phase transformation can provide us a new approach to grain boundary engineering for iron alloys and steels, as well as a new nanocrystalline material produced by magnetic crystallization from the amorphous state. The possibility of engineering applications of enhanced densification using magnetic sintering and magnetic rejuvenation has been discussed for iron powder compacts and deformation-damaged iron alloys, respectively.     

Paconius and the pedestal for Apollo: A case study of error in conceptual design

A classic case history of an engineering failure related by Vitruvius is presented as a paradigm of human error in the design process. It is argued that a familiarity among designers with such case studies could be instrumental in reducing conceptual errors in the design process generally.     

专用瞄准设备自动检定系统

介绍了专用瞄准设备自动检定系统的系统配置、工作原理及软件设计,并对系统的测量不确定度进行了分析和评定。     

Man on the Moon: the technology of lunar exploration

Spurred on by President John F. Kennedy's 1961 speech, which challenged America to place a man on the Moon before the end of the decade, NASA and its industrial contractors succeeded in doing so in July 1969. Delivering three astronauts to the vicinity of the Moon was challenge enough in those early days of the Space Age, but landing a crew on the lunar surface, supporting their science and exploration activities, and returning them to the relative safety of lunar orbit was a separate, equally difficult challenge. The solutions, in the shape of the Apollo lunar module and lunar roving vehicle, are the subjects of this article. Lunar module design and mass reduction are discussed. Power supply and power processing for the lunar module is discussed. The lunar rover is then described with particular emphasis on navigation, operation and performance.     

From the Earth to the Moon: A Freshman Seminar

The seminar course for first‐year undergraduate students, From the Earth to the Moon, deals with both technical and non‐technical aspects of space flight, with particular reference to lunar voyages. The goals of the course are to establish a framework for understanding technology and its applications, to present fundamental principles of science and program management, and to motivate students to learn more about the many facets of engineering. As such, the course introduces numerous issues of systems engineering in a broad context, presenting not only science, technology, and mathematics but also the reasons that these subjects are important. Typically, all of the students in the course have studied physics and/or calculus in high school, though half plan to major in the humanities. Thus, the course has dual roles in exposing liberal arts students to details of technology and engineering students to societal impacts of technology.     

光电设备自动检定数据库管理系统设计

本文介绍了一种光电设备自动检定数据库管理系统的设计方法．论述了该系统数据库的结构,及其建立、管理与维护。着重说明了建立数据库时数据库各表间的关系连接。文中以数据的多种匹配查询具体阐述了自动检定系统数据库的开发与应用。     

图象式自动瞄准系统的研究

本提出一种图象式自动瞄准系统，它采用“电子准星”技术、亚像束细分技术、实现了被测零件轮廓的自动瞄准和自动测量，该系统已成功地应用在万工显图象化和升级改造中，可将万工显测量精度提高一个数量级，同时扩展了原有功能，该方法还可用于各类光电式仪器的自动瞄准和测量。     

红外辐射温度计瞄准的平面辐射源模型

用典型红外辐射温度计的辐射源尺寸效应的实验数据说明不同测量条件下的检定/校准结果的差异可能为其最大允许误差绝对值的数倍。提出具有明确测量条件的平面辐射源瞄准模型和以辐射源前置光阑的方式对于不同空腔黑体辐射源实现相同的等效平面源直径的方法,提出了对光阑的技术特性和放置距离要求,分析表明低温辐射源对光阑的冷却作用可能引起不可忽略的示值降低。采用等效平面源模型的实验结果表明以不同几何条件的空腔黑体辐射源可得到一致的检定结果。讨论了应用平面辐射源模型可能遇到的实际技术问题和解决的对策。     

Optimizing the Utilization of Redundancy of the Apollo Acceptance Checkout Equipment

This article describes a model useful for optimizing the utilization of redundant subsystems in complex test systems. Developed for the Apollo Acceptance Checkout Equipment (ACE), the procedure describes the critical operational modes of the test system; predicts system reliability under various configurations by the use of a Markovian process; and assesses penalties for the use of redundant elements. A ranking scheme then permits management to select the optimum configuration for each critical test.     

ARALL: A materials challenge for the next generation of aircraft

The development of new aircraft is significantly influenced by the introduction of new structural materials. A driving force behind such developments is the perpetual incentive of reducing the aircraft operating costs of which the most important aspects are fule consumption and maintenance.

The structural weight of the aircraft has a high impact on the fuel consumption. Reduction of the weight can be achieved by the introduction of advanced structural design techniques together with new materials which have low density and high (static and dynamic) stress level capabilities. Maintenance costs can be reduced mainly by enlarging the inspection periods of the aircraft. These two aspects, together with the new damage tolerance requirements (FAR and JAR) and durability questions in view of increasing aircraft lives, make the design of an aircraft with low operating costs very complex and difficult.

In this whole process the selection of materials becomes a critical issue. This is illustrated by considering three potential families of materials:

1. - aluminium alloys (both new and conventional)

2. - composites

3. - aramid aluminium laminate (ARALL).

Special attention is given to the development and possible applications of the ARALL material.     

Understanding engineering email: the development of a taxonomy for identifying and classifying engineering work

It is widely believed that email is increasingly becoming the medium where in collaborative engineering work is done; yet, this assumption has not been properly examined. Thus, the extent of engineering information contained in emails and their potential importance within the context of knowledge management is unknown. To address this question, a study was undertaken with a large aerospace propulsion company to investigate the role and characteristics of email communication in engineering design projects. This paper describes the development of a taxonomy and classification method for achieving an understanding of email content and hence its use. The proposed approach is based on relevant techniques for analyzing communication and design text. The method codes the content of e-mail based on a hierarchical scheme by assigning email to categories and sub-categories that denote what topics the email is about, for which communicative purpose it has been sent, and whether it shows evidence of engineering work. The method is applied to a corpus related to the full life cycle of an engineering design project. Metrics for validation are discussed and applied to a sample case. Exemplar findings are presented to illustrate the type of investigations the method supports—including eliciting knowledge about project performance and identifying and accessing engineering knowledge. Finally, lessons from the development of the method, including a discussion of iteratively adaptive variants used to arrive at the final outcome, are discussed.     

Early differentiation of the Earth and the Moon

We examine the implications of new 182W and 142Nd data for Mars and the Moon for the early evolution of the Earth. The similarity of 182W in the terrestrial and lunar mantles and their apparently differing Hf/W ratios indicate that the Moon-forming giant impact most probably took place more than 60Ma after the formation of calcium-aluminium-rich inclusions (4.568Gyr). This is not inconsistent with the apparent U-Pb age of the Earth. The new 142Nd data for Martian meteorites show that Mars probably has a super-chondritic Sm/Nd that could coincide with that of the Earth and the Moon. If this is interpreted by an early mantle differentiation event, this requires a buried enriched reservoir for the three objects. This is highly unlikely. For the Earth, we show, based on new mass-balance calculations for Nd isotopes, that the presence of a hidden reservoir is difficult to reconcile with the combined 142Nd-143Nd systematics of the Earth's mantle. We argue that a likely possibility is that the missing component was lost during or prior to accretion. Furthermore, the 142Nd data for the Moon that were used to argue for the solidification of the magma ocean at ca 200Myr are reinterpreted. Cumulate overturn, magma mixing and melting following lunar magma ocean crystallization at 50-100Myr could have yielded the 200Myr model age.     

论月饼包装

简述了月饼包装的概况,分析了月饼包装中存在的过度包装现象及其危害,并提出了月饼应提倡适度包装的观点.文章对实施适度包装的理论依据进行了分析,指出月饼实施适度包装符合包装的功能要求与绿色包装理论的要求.文章还从选择合适的材料、细分市场、设计合理的结构、利用立法实施适度包装等四方面阐述了月饼实施适度包装的途径.     

一种新型的动态瞄准装置

介绍了一种新型的动态瞄准装置，描述了其光学原理、电路组成等。通过实验验证了其合理性和可行性。