An introduction to the mechanics of DNA

This article gives an overview of recent research on the mechanical properties and spatial deformations of the DNA molecule. Globally the molecule behaves like a uniform elastic rod, and its twisting and writhing govern its compaction and packaging within a cell. Meanwhile high mechanical stresses can induce structural transitions of DNA giving, for example, a phase diagram in the space of the applied tension and torque. Locally, the mechanical properties vary according to the local sequence organization. These variations play a vital role in the biological functioning of the molecule.     

An introduction to the NSPCG software package

NSPCG is the most recent research-oriented software package developed as part of the ITPACK Project at the Center for Numerical Analysis of The University of Texas at Austin. It is designed to solve large sparse systems of linear equations by a variety of different non-symmetric preconditioned conjugate gradient methods. Several different sparse data storage schemes are available for storing the coefficient matrix of the linear system. Matrices with a wide range of structures from highly structured to completely unstructured can be accommodated. To limit memory requirements, the accelerators in the package can be called directly with the matrix stored in a user-defined sparse data storage format (for example, from a particular application) by supplying some user-written routines for certain matrix–vector operations. The main entry point into the package is through a single subroutine call. The various methods are accessed by using a particular naming convention for the first two parameters that in turn selects a preconditioner, an accelerator and a data storage scheme. Some of the basic preconditioners that are available are Jacobi, Incomplete LU Decomposition and Symmetric Successive Overrelaxation as well as block preconditioners. The user can select from a large collection of accelerators such as Conjugate Gradient (CG), Chebyshev (SI, for semi-iterative), Generalized Minimal Residual (GMRES), Biconjugate Gradient Squared (BCGS) and many others. The package is modular so that almost any accelerator can be used with almost any preconditioner. One of the main purposes for the development of the package was to provide a common modular structure for research on iterative methods. The entire package is written in Fortran 77 with vectorization in mind for applications on supercomputers.     

An introduction to quantum turbulence

This paper provides a brief introduction to quantum turbulence in simple superfluids, in which the required rotational motion in the superfluid component is due entirely to the topological defects that are identified as quantized vortices. Particular emphasis is placed on the basic dynamical behaviour of the quantized vortices and on turbulent decay mechanisms at a very low temperature. There are possible analogies with the behaviour of cosmic strings.     

An introduction to the theory of unidimensional unfolding

Despite its 55 year presence in the field of mathematical psychology, the theory of unidimensional unfolding remains an enigma for many psychometricians and applied practitioners. This paper is the first of a three part series; and it aims to introduce unidimensional unfolding theory. The paper begins with a simple hypothetical example presenting an idealised distinction between responses to cumulative and unfolding dichotomous items. This followed by an accessible presentation of the theory of unidimensional unfolding as first articulated by Clyde H. Coombs (1950, 1964). The concept of the single peaked preference function (Coombs and Avrunin, 1977) which underpins unfolding theory is then presented. The article then progresses to the class of Rasch (1960) based IRT models developed by Andrich (1995) and Luo (2001). It was shown these models propose arguments not inconsistent with Coombs's (1964) original theory. The presumption of additive structure in psychological attributes was concluded to be the key weakness of the theories of unidimensional unfolding discussed.     

Liu Zeyuan's philosophy of engineering and technology: An introduction to his Marxist socioeconomic theory

Liu Zeyuan (1940–2020) was a contributing founder to the Northeastern School in Chinese philosophy of technology. As such, he undertook to develop a theory that built on Marxism as the official ideology of the People's Republic of China. Following an overview of Liu's life and work, this article introduces the Marxist socioeconomic theory that served as a framework for his research. It then describes how he used this theory to reflect on the essential features and historical evolution of engineering and technology along with his analyses of issues related to innovation, ethics, and governance. It includes some reflections on how Liu's thought can be related to other philosophies of engineering and technology both inside and outside China.     

膜技术在石化工业中的应用浅谈

简要介绍了膜技术在石化工业中的应用     

一种隔离损伤的桁架结构性态识别方法

实际工程中出现的损伤往往具有非线性特征,比如裂缝开合导致结构刚度呈现明显的双线性特性。采用简单的线性模型会遗漏与损伤相关的非线性信息,进而影响到损伤识别结果的可靠性。为解决上述问题,该文提出基于马尔科夫状态转移向量自回归模型(MSVAR)的非线性损伤识别方法。该方法假定损伤会导致结构振动响应出现非线性特征,利用MSVAR模型隐状态平滑概率能够反映数据非线性变化的特点,构造信息熵作为损伤预警指标监测结构损伤状态。MSVAR模型的自回归系数包含损伤位置信息,可据此构造损伤定位向量确定裂缝位置,以裂缝位置处的层间位移(平滑概率由0突变到100%时)表征裂缝宽度。最后通过数值算例和模型试验验证该文所提方法在裂缝类型损伤识别的有效性。     

An introduction to high-voltage electron microscopy

The various features of high voltage electron microscopy are examined in some detail, including basic features of the instrument such as lens aberrations, etc and more particularly, the effect of the microscope voltage on the behaviour of crystalline specimens, both in respect of the formation of diffraction contrast from defects and the production of radiation damage.High accelerating voltages (i.e. 500 to 1000 kV) enable thicker foils (1 to 2 m of medium atomic number materials and 4 to 8 m of aluminium) to be used so that the foil behaviour is more typical of bulk material. In addition, diffraction patterns can be obtained from smaller precipitates and sharp dark field micrographs can be produced without beam tilting.The major disadvantage is probably the formation of radiation damage by displacement of atoms when the electron energy exceeds a threshold value.     

An introduction to structural health monitoring

The process of implementing a damage identification strategy for aerospace, civil and mechanical engineering infrastructure is referred to as structural health monitoring (SHM). Here, damage is defined as changes to the material and/or geometric properties of these systems, including changes to the boundary conditions and system connectivity, which adversely affect the system's performance. A wide variety of highly effective local non-destructive evaluation tools are available for such monitoring. However, the majority of SHM research conducted over the last 30 years has attempted to identify damage in structures on a more global basis. The past 10 years have seen a rapid increase in the amount of research related to SHM as quantified by the significant escalation in papers published on this subject. The increased interest in SHM and its associated potential for significant life-safety and economic benefits has motivated the need for this theme issue.This introduction begins with a brief history of SHM technology development. Recent research has begun to recognize that the SHM problem is fundamentally one of the statistical pattern recognition (SPR) and a paradigm to address such a problem is described in detail herein as it forms the basis for organization of this theme issue. In the process of providing the historical overview and summarizing the SPR paradigm, the subsequent articles in this theme issue are cited in an effort to show how they fit into this overview of SHM. In conclusion, technical challenges that must be addressed if SHM is to gain wider application are discussed in a general manner.     

Conceptual approach to introduction of information technology into the field of simulation

We consider results of research by the faculty for design and production of radio equipment at Penza State University; the research was concerned with development of methods, models, algorithms, and software packages for investigating complex mechanical systems, technologies, and simulation of physical processes. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 7–11, May, 1999.     

浅谈真空冷冻干燥技术

经过长期从事进口真空冷冻干燥设备（VIRTIS 500SRC-18X）和ATLAS（RAY-50）的生产实践，通过学习总结了真空冷冻干燥的三个阶段，这对研究某一食品真空冷冻干燥工艺会有所帮助的。     

An introduction to statistical parametric speech synthesis

Statistical parametric speech synthesis, based on hidden Markov model-like models, has become competitive with established concatenative techniques over the last few years. This paper offers a non-mathematical introduction to this method of speech synthesis. It is intended to be complementary to the wide range of excellent technical publications already available. Rather than offer a comprehensive literature review, this paper instead gives a small number of carefully chosen references which are good starting points for further reading.     

An introduction to BEM by integral transforms

The paper provides a new method for obtaining the fundamental integral representation used in BEM. The method is based on integral transforms and can be applied to all linear differential equations with constant coefficients. Some explicit formulae pertaining to potential problems, linear elasticity and low Reynolds number flows are derived.     

An introduction to Chinese manufacturing research institutions

The manufacturing environment has dramatically changed in the last few years. Worldwide competition among manufacturers and the development of new manufacturing technologies have contributed to today's competitive situation in many manufacturing areas. Advanced computer technology is the driver that has made global manufacturing competition possible. In this paper, the current research of advanced manufacturing technology at major institutions in China is introduced.     

An introduction to crystal lattice imaging with the electron microscope

The direct imaging of a crystal lattice has intrigued electron microscopists for many years. With present-day 100 kV transmission electron microscopes, crystal lattice spacings of 3 Å or less are readily imaged. What is of interest, of course, is the way in which defects perturb the atoms in the crystal lattice. It is the purpose of this introductory paper to consider how the experimental parameters, over which the microscopist has some control, can be adjusted so that the lattice image contrast can be maximized and, more important, so that it can be interpreted in terms of specimen structure.