刨煤机平面振动的数学建模与仿真

为了降低刨头的振动,提高刨煤机的工作性能,通过简化和假设,应用牛顿定律建立了刨煤机在垂直煤壁方向振动和在水平面扭转振动的数学模型,通过对刨煤机的实体模型进行简化并导入Adams软件,得到了刨头沿垂直煤壁方向和平面扭转振动的仿真曲线,为研究刨煤机的振动、改进设计、合理确定刨煤机的参数提供了理论依据。     

A simple check of the time homogeneity of Markov chains

In this paper we consider a population where the state of each individual follows a Markov chain. If the population is recorded for a very few periods only, it is still possible to estimate the transition matrix and to make projections into the far future. These forecasts are sensible if the chains are time homogeneous, but this is difficult to check if only a few periods are observed. We suggest a simple method to check this assumption, and obtain an upper bound on the time the process can have been time homogeneous. The method is also applied to a second-order Markov chain and to the mover-stayer model. AMS subject classification (1980): Primary 62M05, Secondary 62M20.     

The normativity of artefacts

Part of the distinction between artefacts, objects made by humans for particular purposes, and natural objects is that artefacts are subject to normative judgements. A drill, say, can be a good drill or a poor drill, it can function well or correctly or it can malfunction. In this paper I investigate how such judgements fit into the domain of the normative in general and what the grounds for their normativity are. Taking as a starting point a general characterization of normativity proposed by Dancy, I argue how statements such as ‘this is a good drill’ or ‘this drill is malfunctioning’ can be seen to express normative facts, or the content of normative statements. What they say is that a user who has a desire to achieve a particular relevant outcome has a reason to use, or not to use, the artefact in question. Next this analysis is extended to show that not just statements that say that an artefact performs its function well or poorly, but all statements that ascribe a function to an artefact can be seen as expressing a normative fact. On this approach the normativity of artefacts is analyzed in terms of reasons on grounds of practical, and to a lesser extent theoretical, rationality. I close by investigating briefly to what extent reasons on moral grounds are, in the analysis adopted here, involved in the normativity of artefacts.     

Impact of climate change on wetland ecosystems: A critical review of experimental wetlands

Climate change is identified as a major threat to wetlands. Altered hydrology and rising temperature can change the biogeochemistry and function of a wetland to the degree that some important services might be turned into disservices. This means that they will, for example, no longer provide a water purification service and adversely they may start to decompose and release nutrients to the surface water. Moreover, a higher rate of decomposition than primary production (photosynthesis) may lead to a shift of their function from being a sink of carbon to a source. This review paper assesses the potential response of natural wetlands (peatlands) and constructed wetlands to climate change in terms of gas emission and nutrients release. In addition, the impact of key climatic factors such as temperature and water availability on wetlands has been reviewed. The authors identified the methodological gaps and weaknesses in the literature and then introduced a new framework for conducting a comprehensive mesocosm experiment to address the existing gaps in literature to support future climate change research on wetland ecosystems. In the future, higher temperatures resulting in drought might shift the role of both constructed wetland and peatland from a sink to a source of carbon. However, higher temperatures accompanied by more precipitation can promote photosynthesis to a degree that might exceed the respiration and maintain the carbon sink role of the wetland. There might be a critical water level at which the wetland can preserve most of its services. In order to find that level, a study of the key factors of climate change and their interactions using an appropriate experimental method is necessary. Some contradictory results of past experiments can be associated with different methodologies, designs, time periods, climates, and natural variability. Hence a long-term simulation of climate change for wetlands according to the proposed framework is recommended. This framework provides relatively more accurate and realistic simulations, valid comparative results, comprehensive understanding and supports coordination between researchers. This can help to find a sustainable management strategy for wetlands to be resilient to climate change.     

Impact of climate change on wetland ecosystems: A critical review of experimental wetlands

Climate change is identified as a major threat to wetlands. Altered hydrology and rising temperature can change the biogeochemistry and function of a wetland to the degree that some important services might be turned into disservices. This means that they will, for example, no longer provide a water purification service and adversely they may start to decompose and release nutrients to the surface water. Moreover, a higher rate of decomposition than primary production (photosynthesis) may lead to a shift of their function from being a sink of carbon to a source. This review paper assesses the potential response of natural wetlands (peatlands) and constructed wetlands to climate change in terms of gas emission and nutrients release. In addition, the impact of key climatic factors such as temperature and water availability on wetlands has been reviewed. The authors identified the methodological gaps and weaknesses in the literature and then introduced a new framework for conducting a comprehensive mesocosm experiment to address the existing gaps in literature to support future climate change research on wetland ecosystems. In the future, higher temperatures resulting in drought might shift the role of both constructed wetland and peatland from a sink to a source of carbon. However, higher temperatures accompanied by more precipitation can promote photosynthesis to a degree that might exceed the respiration and maintain the carbon sink role of the wetland. There might be a critical water level at which the wetland can preserve most of its services. In order to find that level, a study of the key factors of climate change and their interactions using an appropriate experimental method is necessary. Some contradictory results of past experiments can be associated with different methodologies, designs, time periods, climates, and natural variability. Hence a long-term simulation of climate change for wetlands according to the proposed framework is recommended. This framework provides relatively more accurate and realistic simulations, valid comparative results, comprehensive understanding and supports coordination between researchers. This can help to find a sustainable management strategy for wetlands to be resilient to climate change.     

基因组学:生命科学的系统化研究和生物世纪的科学革命

DNA(脱氧核糖核酸)是基因的“文字”，基因是生命的“语言”，生命的“剧本”用基因来编写。基因组学则是生命剧本的“导演”。DNA序列因此就成了舞台剧本。基因组学是一门大规模地、系统地研究物种全部基因和它们生物学意义和运动的学问。如今，我们正站在一个革命性的转折点上，也就是基因组学正处于生命科学的领导前沿。我们不该为此恐慌、怀疑甚或因而改变方向。获得一个物种的基本的基因组信息，比如基因的图谱及其在细胞中的产物，是我们了解该物种生物学意义的第一步。我们应该根据基础研究、经济效益和社会的需要来考虑测序日程上物种的先后次序。     

Misuses of biology in the context of the paranormal

Public suspicion of science stems from science's challenging of perceptions and myths about reality, and a public fear of new technology. The result is a susceptibility to pseudoscience. In claiming that creation 'science' is as valid as evolution the creationists misquote scientists and seek to spread their own 'scientific' myths concerning a young age for the earth, an act of creation based on a particular literalist interpretation of the Christian Bible and a single worldwide flood. They use methods of debate and politics, rather than scientific research. A selection of their arguments is examined and the nature of the evidence for evolution is discussed. Problems with the creation 'science' model are noted. In the myth of the hundredth monkey phenomenon, original research is misquoted to denigrate scientific research and support sentimental ideas of paranormal events. The misuse of science is seen as damaging to society because it reduces the effective gathering and application of scientific information. However, pseudoscience provides a valuable guide to gaps in public scientific education.     

Another parting of the ways: Intersubjectivity and the objectivity of science

Michael Friedman defines the scientific enterprise as an ongoing project with a dynamics of reason that persists through scientific revolutions: The coherence and continuity of science owes to a communicative rationality that is operative at all times. It assures us of our shared objective world by transforming subjective points of view into intersubjectively binding agreements. Though it takes a very broad approach epistemologically, this conception of science may yet be too narrow in respect to notions of objectivity. It excludes a prominent mode of knowledge production that might be called technoscientific. This exclusion becomes particularly evident in Friedman’s discussion of Heidegger as a critic of Cassirer and Carnap and as a critic of objectivity as “universal validity” of scientific propositions. If one tends to Heidegger’s own account of objectivity, one encounters a non-propositional notion of truth. Science is seen as a technology that brings forth phenomena and processes. Accordingly, even where modern physics appears to be concerned primarily with the formulation of theories and the testing of hypotheses, it uses mathematical and representational techniques to conceive and create the modern world. And more powerfully than intersubjective agreement, technologies assure us of the unity and objectivity of our simultaneously social as well as natural world. There may be good reasons to hold fast to the close affiliation of communicative rationality, science, and enlightenment. However, to the extent that it turns a blind eye to technoscientific knowledge production and the technological character of science, a philosophy of technoscience needs to develop an alternative perspective on questions of objectivity, explanation, inference, or validation.     

Maimon's criticism of Kant's doctrine of mathematical cognition and the possibility of metaphysics as a science

The aim of this paper is to discuss Maimon's criticism of Kant's doctrine of mathematical cognition. In particular, we will focus on the consequences of this criticism for the problem of the possibility of metaphysics as a science. Maimon criticizes Kant's explanation of the synthetic a priori character of mathematics and develops a philosophical interpretation of differential calculus according to which mathematics and metaphysics become deeply interwoven. Maimon establishes a parallelism between two relationships: on the one hand, the mathematical relationship between the integral and the differential and on the other, the metaphysical relationship between the sensible and the supersensible. Such a parallelism will be the clue to the Maimonian solution to the Kantian problem of the possibility of metaphysics as a science.     

A semi-automatic computerized analysis of tracks of ciliates

Summary The behavior of Protozoa can be studied by using the ethogram as a conceptual tool capable of giving an almost complete picture of the motor biology of these microorganisms. A new semi-automatic, computerized method for drawing ethograms is described here: it allows a time-saving of about 70%, in comparison with the similar manual procedure. Microorganism movements are photographed by a Pentax LX camera from the screen of a TV monitor, connected to the stereomicroscope by a TV camera, and resolved into single images using a stroboscopic apparatus. The pictorial data are introduced into the computer by means of a digitizing tablet, and the track analysis is performed semi-automatically. The measurements recorded are then processed using a commercial statistics package in order to obtain a general view of the quantitative parameters of each ethogram.     

Ergodic Theory, Interpretations of Probability and the Foundations of Statistical Mechanics

The traditional use of ergodic theory in the foundations of equilibrium statistical mechanics is that it provides a link between thermodynamic observables and microcanonical probabilities. First of all, the ergodic theorem demonstrates the equality of microcanonical phase averages and infinite time averages (albeit for a special class of systems, and up to a measure zero set of exceptions). Secondly, one argues that actual measurements of thermodynamic quantities yield time averaged quantities, since measurements take a long time. The combination of these two points is held to be an explanation why calculating microcanonical phase averages is a successful algorithm for predicting the values of thermodynamic observables. It is also well known that this account is problematic.This survey intends to show that ergodic theory nevertheless may have important roles to play, and it explores three other uses of ergodic theory. Particular attention is paid, firstly, to the relevance of specific interpretations of probability, and secondly, to the way in which the concern with systems in thermal equilibrium is translated into probabilistic language. With respect to the latter point, it is argued that equilibrium should not be represented as a stationary probability distribution as is standardly done; instead, a weaker definition is presented.     

The methodological defense of realism scrutinized

I revisit an older defense of scientific realism, the methodological defense, a defense developed by both Popper and Feyerabend. The methodological defense of realism concerns the attitude of scientists, not philosophers of science. The methodological defense is as follows: a commitment to realism leads scientists to pursue the truth, which in turn is apt to put them in a better position to get at the truth. In contrast, anti-realists lack the tenacity required to develop a theory to its fullest. As a consequence, they are less likely to get at the truth.My aim is to show that the methodological defense is flawed. I argue that a commitment to realism does not always benefit science, and that there is reason to believe that a research community with both realists and anti-realists in it may be better suited to advancing science. A case study of the Copernican Revolution in astronomy supports this claim.     

Metabolic activity of goat adipose tissue at the end of gestation and at the beginning of lactation: level of deoxyribouncleic acid content and lipoprotein lipase activity]

In the goat the passage from late pregnancy to early lactation is accompanied by a decrease of the epiploon lipoprotein lipase activity and an increase in the epiploon DNA content. The between-goat variations allow us to emphasize a linear relation between the lipoprotein lipase activity decrease and the reduction of the epiploon volume, expressed on a DNA basis. These parameters, used as indicators of the adipose tissue metabolic status, could contribue to the determination of a feeding strategy adapted to high yield milking Ruminants.     

Outline of a dynamical inferential conception of the application of mathematics

We outline a framework for analyzing episodes from the history of science in which the application of mathematics plays a constitutive role in the conceptual development of empirical sciences. Our starting point is the inferential conception of the application of mathematics, recently advanced by Bueno and Colyvan (2011). We identify and discuss some systematic problems of this approach. We propose refinements of the inferential conception based on theoretical considerations and on the basis of a historical case study. We demonstrate the usefulness of the refined, dynamical inferential conception using the well-researched example of the genesis of general relativity. Specifically, we look at the collaboration of the physicist Einstein and the mathematician Grossmann in the years 1912–1913, which resulted in the jointly published “Outline of a Generalized Theory of Relativity and a Theory of Gravitation,” a precursor theory of the final theory of general relativity. In this episode, independently developed mathematical theories, the theory of differential invariants and the absolute differential calculus, were applied in the process of finding a relativistic theory of gravitation. The dynamical inferential conception not only provides a natural framework to describe and analyze this episode, but it also generates new questions and insights. We comment on the mathematical tradition on which Grossmann drew, and on his own contributions to mathematical theorizing. The dynamical inferential conception allows us to identify both the role of heuristics and of mathematical resources as well as the systematic role of problems and mistakes in the reconstruction of episodes of conceptual innovation and theory change.     

Three denials of time in the interpretation of canonical gravity

The analysis of the temporal structure of canonical general relativity and the connected interpretational questions with regard to the role of time within the theory both rest upon the need to respect the fundamentally dual role of the Hamiltonian constraints found within the formalism. Any consistent philosophical approach towards the theory must pay dues to the role of these constraints in both generating dynamics, in the context of phase space, and generating unphysical symmetry transformations, in the context of a hypersurface embedded within a solution. A first denial of time in the terms of a position of reductive temporal relationalism can be shown to be troubled by failure on the first count, and a second denial in the terms of Machian temporal relationalism can be found to be hampered by failure on the second. A third denial of time, consistent with both of the Hamiltonian constraints roles, is constituted by the implementation of a scheme for constructing observables in terms of correlations and leads to a radical Parmenidean timelessness. The motivation for and implications of each of these three denials are investigated.     

On the necessary truth of the laws of classical mechanics

The idealization of primitive mechanical experience is shown to lead to four mutually related formulations of classical mechanics based on connections, action at a distance, stresses, and collisions. For a given structure of spacetime and a given characterization of mechanical systems, fundamental laws (including Newton's law of acceleration and d’Alembert's principle) are derived from a few general principles regarding the comprehensibility of motion. Special emphasis is placed on the “secular principle,” according to which the evolution of a system at the relevant time scale should not depend on finer details of the applied forces.     

Walls of resonance: Institutional history and the buildings of the University of Manchester

The built environments of universities are useful for telling stories about their development. Exteriors – walls, windows, doorways, the relative positioning of different facilities – are particularly suited to broad institutional narratives: the rise and decline of scientific disciplines, for instance, or the institution’s changing relationship with benefactors and the wider public. Exteriors are also conveniently accessible to public audiences.This paper explores the possibilities through the case of the University of Manchester. The approach is in a sense the converse of industrial archaeology, which seeks to understand the functioning of a site from what survives of its material form: here, we have begun with knowledge gained largely from document sources, and aim to bring it to life for visitors by pointing to the material consequences. Connecting doors and architectural symmetries illustrate founding unifications and alliances; infilling and glassing-over, constrained expansion; grand but obscured frontages, displaced priorities.Populating the site with accounts of its lived existence is a powerful tool to communicate history, but it is important not to create an ‘official’ memorialisation: audiences often know the site at first hand, and may question any received version. I conclude by calling for a reflexive treatment, mapping the histories of the stories themselves.     

Evaluation of models for the mechanism of action of 4-hydroxyphenylpyruvate dioxygenase

Summary 4-Hydroxyphenylpyruvic acid was oxygenated with various complexes of oxygen with Fe²⁺, superoxide ion, hydroperoxide anion, triplet and singlet oxygen. Oxidation occurred giving varying amounts of the 4-hydroxy derivatives of benzaldehyde, benzoic acid, phenol, phenylacetic acid and 4-carboxymethylquinone, but no homogentisic acid. 4-Hydroxyphenylperacetic acid was prepared and shown not to undergo self-oxidation. Its ferrous salt decomposed to 4-hydroxybenzyl alcohol. It is concluded that thea-keto carboxylic function is the site of oxygenation in the enzyme process and that a trioxalanone rather than a peracid intermediate may be implicated.Acknowledgments. We thank a referee for drawing our attention to the work of Hawkinsin and we are indebted to the Swiss National Science Foundation for the support of this work (grant No 2.418.0.79).     

Evaluating Forecasts of a Vector of Variables: A German Forecasting Competition

In this paper we explore methodologies appropriate for evaluating a forecasting competition when the participants predict a number of variables that may be related to each other and are judged for a single period. Typically, forecasting competitions are judged on a variable‐by‐variable basis, but a multivariate analysis is required to determine how each competitor performed overall. We use three different multivariate tests to determine an overall winner for a forecasting competition for the German economy across 25 different institutions for a single time period using a vector of eight key economic variables. We find that neglecting the cross‐variable relationships greatly alters the outcome of the forecasting competition. Copyright © 2016 John Wiley & Sons, Ltd.     

Gender and philosophy of science: The case of Mary Hesse

This article is composed of two intertwining narratives. The first is a discussion of the concept of gender in relation to philosopher of science Mary Hesse's theoretical contributions and academic experiences. The second narrative takes issue with the gender concept at a more general level and particularly to discuss its strengths and limits. The article alternates between a discussion of different claims from gender theorists and a presentation of Mary Hesse's academic experiences. I conclude that although the gender concept has, until now, only been used in an asymmetrical sense, i.e., negatively linked to women's careers and positively to men's, it will not necessarily be identically used in the future. Both empirical findings and conceptual changes may make room for a more differentiated understanding of gender.