生产率悖论与中美两国信息技术投资效果比较

信息技术的生产率悖论问题已经讨论了几十年,过去这个领域的研究主要限制在美国,但是信息技术生产率悖论在其它国家和地区的适用性如何仍然是有争议的。本研究的重点在于用事件分析法研究发达国家和发展中国家信息技术投资效果的不同。以中国作为发展中国家的代表,美国作为发达国家的代表,对上个世纪90年代后期的IT投资的影响进行了对比。结果发现,中国企业的IT投资对企业的市场价值产生了巨大的影响,但在美国企业的研究中并未发现此现象。这表明在不同发展水平的国家中,IT扮演了不同的角色,从而说明生产率悖论不是一个全球化的问题。该发现与Baumol的不平衡经济增长理论相吻合,此理论亦可作为生产率悖论的一个可信的解释。     

Taguchi methods in practice: An analysis of Goh's paradox

The background of ‘Goh's paradox’ in connection with the application of the common version of Genichi Taguchi's parameter design routine is examined. A detailed case study is used to show how the paradox can be resolved, as well as to assess the probability of success of marginal analysis in Taguchi's prescribed procedure for quality and reliability improvement.     

Boxfish swimming paradox resolved: forces by the flow of water around the body promote manoeuvrability

The shape of the carapace protecting the body of boxfishes has been attributed an important hydrodynamic role in drag reduction and in providing automatic, flow-direction realignment and is therefore used in bioinspired design of cars. However, tight swimming-course stabilization is paradoxical given the frequent, high-performance manoeuvring that boxfishes display in their spatially complex, coral reef territories. Here, by performing flow-tank measurements of hydrodynamic drag and yaw moments together with computational fluid dynamics simulations, we reverse several assumptions about the hydrodynamic role of the boxfish carapace. Firstly, despite serving as a model system in aerodynamic design, drag-reduction performance was relatively low compared with more generalized fish morphologies. Secondly, the current theory of course stabilization owing to flow over the boxfish carapace was rejected, as destabilizing moments were found consistently. This solves the boxfish swimming paradox: destabilizing moments enhance manoeuvrability, which is in accordance with the ecological demands for efficient turning and tilting.     

Effect of cannibalism on a predator–prey system with nutritional value: a model based study

Enrichment of a simple predator–prey system results in the destruction of stable steady state and further enrichment leads to the extinction of the species, which is a classical problem in ecology and known as the paradox of enrichment. The Paradox of enrichment is a controversial issue. Most theoretical studies show the destabilization of predator–prey system due to enrichment, but there is a discrepancy between the empirical evidence and theoretical predictions. In spite of the debate and cross-debate, research is still being carried out on the paradox of enrichment (16 papers and nearly 500 citations in 2008), which in general does not include the effect of cannibalism. Here we present a simple predator–prey system in the presence of cannibalism among predators and offer a novel resolution to the paradox of enrichment. The concept of nutritional value is introduced by many authors to resolve the issue. It is observed that even in the face of sufficient enrichment the system remains stable in the vicinity of critical nutritional value. In the case of a lower cannibalism rate we also observe similar kinds of behaviour, but for a higher cannibalism rate, the system remains always stable and does not depend upon the nutritional value of prey, i.e. paradox of enrichment does not hold at all in such a situation. We also observe that cannibalism can have a positive as well as a negative effect on population abundance, depending on the cannibalism rate.     

A paradox in the crossover of the mechanisms causing the hysteresis in long,thin-film superconductors

We point out an apparent paradox encountered in the region where the temperature of a voltage-sustaining film at the upper critical current crosses its Tin concerning the crossover of the two dominant heating mechanisms currently used to account for the lower critical currents observed on the hysteretic current-voltage characteristics of long, thin-film superconductors at varying high power levels. We explore a possible solution of this paradox by carefully examining the relevant heating models and available experimental observations.     

A note on Lindley's paradox

Lindley's paradox epitomizes the conflict between Bayesian and frequentist evidences in hypothesis testing. We scrutinize the point null approximation assumption using the interval null and the smooth formulations. Along with numerical calculation, under the smooth null formulation, we have found that Lindley's paradox prevails relatively independent of smoothness of the target function. However, it is less drastic as suggested earlier. The research is supported by Taiwan NSC 91-2118-M-259-003     

A Process-Based Explanation of the Psychic Distance Paradox: Evidence from Global Virtual Teams

Previous research has found evidence of a counter-intuitive positive relationship between psychic distance and performance, which has been labeled the “psychic distance paradox”. However, there is a dearth of literature explaining the causal mechanisms that elucidates such a positive relationship. Studying the effect of team-level psychic distance on the performance of global virtual teams, we build on the input-process-outcome framework of team research, which allows the integration of process variables to provide new insights into the underlying coherences of the psychic distance paradox. These variables include the team members’ expectation of challenges as well as the level of team effort toward the task. The team members’ motivational cultural intelligence is introduced to the model as a moderating factor. The data support the hypothesized causal path. The findings start unveiling the psychic distance paradox through the integration of the literatures on psychic distance and global virtual teams.     

An information trail model for capturing human behaviour in artefact creation and use in complex work systems

This article presents an information trail model. The model is a method for uncovering information transformation using artefacts in complex work systems. We use a patient care scenario in a hospital emergency department to illustrate theoretical, methodological and design elements of the model. In a complex system, humans create and manage complexity, a paradox. The information trail model proposes that humans manage the paradox by creating and evolving artefacts and information cues. They organise purposefully through self-organisation and stigmergical behaviour. Information trail model states that humans leave trails of information as signs or symbols, and the piecing together and transformation of which will lead to final goals. Information trails contain work attributes and strategies, which can be utilised in work system design.     

A regularization study of some softening beam problems with an implicit gradient plasticity model

The modelling of plastic beams experiencing softening is studied. The homogeneous cantilever beam loaded by a concentrated force at its extremity is considered. This simple structural problem with gradient bending moment allows an analytical treatment of the evolution problem. A gradient plasticity model is developed in order to overcome Wood’s paradox. Surprisingly, explicit gradient plasticity models do not eliminate this paradox, since the beam response is found to be not continuous with respect to the loading parameter. A new implicit gradient plasticity model is used in this paper. It is shown that the new regularized problem is well-posed. Closed-form solutions of the elastoplastic deflection are finally derived. These results are valid for the beam bending problem, but also for the simple analogy of the bar subjected to distributed axial force.     

Evaluating the performance of US manufacturing and service operations in the presence of IT: a Bayesian stochastic production frontier approach

In this paper, we evaluate the performance of US manufacturing and service operations in the presence of information technology (IT) as measured by technical efficiency, using firm-level data from 133 companies over the period from 1999 to 2009. To gain insight into the phenomenon of the ‘IT productivity paradox’, or the history of inconsistent findings in the existing literature, we employ a Bayesian stochastic production frontier approach to model the relationship between performance and technical efficiency at the firm, industry and sector levels. Some results are indicative of a slight advantage of the manufacturing sector over the service sector in terms of technical efficiency and a significant positive contribution of IT-investment to firm output. However, other results do suggest the productivity paradox, because of a lack of any definitive association of high IT investment levels with either high- or low-technical efficiency. Indeed, the findings of this study suggest that the origin of some portion of the IT productivity paradox may exist at the industry level, in that the relationship between extreme levels of IT-investment and extreme levels of technical efficiency appear to work differently in sufficiently different industries.     

A Bayesian analysis of classical hypothesis testing

Summary The procedure of maximizing the missing information is applied to derive reference posterior probabilities for null hypotheses. The results shed further light on Lindley’s paradox and suggest that a Bayesian interpretation of classical hypothesis testing is possible by providing a one-to-one approximate relationship between significance levels and posterior probabilities.     

How Do People Value Data Utilization?: An Empirical Analysis Using Contingent Valuation Method in Japan

In this study, we tested the following three hypotheses regarding the data utilization of online services: 1) Service users are concerned about the data utilization of service providers, and there exists a privacy paradox. 2) Consumer evaluations of data utilization are diverse, and some service users are positive about data utilization. 3) People with familiarity with the Internet are more positive about data utilization. In order to quantitatively measure people's evaluation of data utilization, we used contingent valuation method (CVM) in a survey by questionnaire of 5986 people to find out their willingness to pay for data utilization. The results of the empirical analysis show that all hypotheses were supported. We can obtain the following two policies and service providers implications. First, there is a privacy paradox with respect to data utilization, so the service providers need to create an environment where people can choose the level of data utilization. Second, it is necessary to design a rule that takes diverse values into account.     

Many ways to stay in the game: individual variability maintains high biodiversity in planktonic microorganisms

In apparent contradiction to competition theory, the number of known, coexisting plankton species far exceeds their explicable biodiversity—a discrepancy termed the Paradox of the Plankton. We introduce a new game-theoretic model for competing microorganisms in which one player consists of all organisms of one species. The stable points for the population dynamics in our model, known as strategic behaviour distributions (SBDs), are probability distributions of behaviours across all organisms which imply a stable population of the species as a whole. We find that intra-specific variability is the key characteristic that ultimately allows coexistence because the outcomes of competitions between individuals with variable competitive abilities are unpredictable. Our simulations based on the theoretical model show that up to 100 species can coexist for at least 10 000 generations, and that even small population sizes or species with inferior competitive ability can survive when there is intra-specific variability. In nature, this variability can be observed as niche differentiation, variability in environmental and ecological factors, and variability of individual behaviours or physiology. Therefore, previous specific explanations of the paradox are consistent with and provide specific examples of our suggestion that individual variability is the mechanism which solves the paradox.     

The informative converse paradox: Windows into the unknown

Model-based interpretation of empirical data is useful. But unanticipated phenomena (interferences) can give erroneous model parameter estimates, leading to wrong interpretation. However, for multi-channel data, interference phenomena may be discovered, described and corrected for, by analysis of the lack-of-fit residual table — although with a strange limitation, which is here termed the Informative Converse paradox: When a data table (rows × columns) is approximated by a linear model, and the model-fitting is done by row-wise regression, it means that only the column-wise interference information can be correctly obtained, and vice versa. These “windows into the unknown” are here explained mathematically. They are then applied to multi-channel mixture data — artificial simulations as well as spectral NIR powder measurements — to demonstrate discovery after incomplete row-wise curve fitting and column-wise multivariate regression. The analysis shows how the Informative Converse paradox is the basis for selectivity enhancement in multivariate calibration. Data-driven model expansion for statistical multi-response analyses (ANOVA, N-way models etc.) is proposed.     

The Janus faces of nanoparticles

There is an paradox apparent in the fact that nanoparticles have potential use in nanomedicine for imaging and therapy, whereas combustion-derived NP are thought to be responsible for adverse health effects of air pollution. The nanotechnology industry is in the process of producing a number of new nanoparticles which are as-yet unquantified with regard to both hazard and potential for human exposure. The toxicology of combustion-derived nanoparticles is developing and there is now considerable understanding of how they might drive both adverse lung and cardiovascular effects, including the importance of small size, large relative surface area and oxidative stress. Medicinal nanoparticles are being developed and tested on a case-by-case basis using testing protocols from biomaterials and drug safety and with regard to risk-benefit. There are considerable differences in physical and chemical properties and biodegradability between medicinal nanoparticles and the industrial and combustion-derived nanoparticles studied by particle toxicologists and we would anticipate that the bulk of medicinal NP types will be of low toxicity. However, to resolve the nanoparticle paradox there is a need to advance understanding of the characteristics that control acute and chronic toxicity, translocation, biodegradation and elimination of all of the types of particles likely to gain access to the human body. Much would be gained in this area by collaboration between particle toxicologists and nanopharmacologists.     

The key role of collaborative work in the growth of Brazilian science in the last ten years

The Brazilian scientific production and its international impact increased considerably in the last 10 years. This increase occurred in spite of a reduction in the resources for science in the same period. The data show that the explanation for this apparent paradox lies in the active process of international and national collaboration which increased in this same period. Collaborative work was supported by several programs of the Brazilian agencies. Advantages and possible drawbacks of the intensification of scientific collaboration for the Brazilian science are discussed.     

Causal Inference

Causal inference is a powerful modeling tool for explanatory analysis, which might enable current machine learning to become explainable. How to marry causal inference with machine learning to develop explainable artificial intelligence (XAI) algorithms is one of key steps toward to the artificial intelligence 2.0. With the aim of bringing knowledge of causal inference to scholars of machine learning and artificial intelligence, we invited researchers working on causal inference to write this survey from different aspects of causal inference. This survey includes the following sections: “Estimating average treatment effect: A brief review and beyond” from Dr. Kun Kuang, “Attribution problems in counterfactual inference” from Prof. Lian Li, “The Yule–Simpson paradox and the surrogate paradox” from Prof. Zhi Geng, “Causal potential theory” from Prof. Lei Xu, “Discovering causal information from observational data” from Prof. Kun Zhang, “Formal argumentation in causal reasoning and explanation” from Profs. Beishui Liao and Huaxin Huang, “Causal inference with complex experiments” from Prof. Peng Ding, “Instrumental variables and negative controls for observational studies” from Prof. Wang Miao, and “Causal inference with interference” from Dr. Zhichao Jiang.     

A peculiarity in measuring the disperse drop composition in a two-phase stream

The paradox of repeated drop breakup in a two-phase stream is considered. A method of measuring their slip coefficients is proposed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 6, pp. 995–999, June, 1977.     

Non-local behavior of plastic softening beams

Summary This paper deals with the modelling of a plastic beam experiencing softening. This kind of behaviour is observed in steel or reinforced concrete structural members undergoing large rotation amplitudes, which may occur typically for civil engineering structures in the seismic area. The homogeneous cantilever beam loaded by a concentrated force at its extremity is considered. This simple structural problem with gradient bending moment allows an analytical treatment of the evolution problem. It is shown that a local plastic softening model makes the evolution problem ill-posed. Moreover, if we require the plastic curvature to be a continuous variable of the spatial coordinate, Wood’s paradox is encountered. A non-local gradient plastic model is developed in order to overcome this paradox. However classical gradient plastic models may not eliminate the ill-posedness since the beam response may not be continuous with respect to the loading parameter. The new gradient plastic model, presented in this paper, is similar to previous classical gradient models. The main difference is the yield moment considered as a non-local material parameter. This permits to ensure continuity between the elastic and the plastic regions during the loading process. These solutions are controlled by the ratio between the material length and the geometrical length of the beam. The new evolution problem may remain ill-posed as it possesses a finite number of solutions (which can be unique). Closed-form solutions of the unknown deflection are given.     

The energy landscape as a unifying theme in molecular science

The potential energy surface (PES) underlies most calculations of structure, dynamics and thermodynamics in molecular science. In this contribution connections between the topology of the PES and observable properties are developed for a coarse-grained model of virus capsid self-assembly. The model predicts that a thermodynamically stable, kinetically accessible icosahedral shell exists for pentameric building blocks of the right shape: not too flat and not too spiky. The structure of the corresponding PES is probably common to other systems where directed searches avoid Levinthal's paradox, such as 'magic number' clusters, protein folding and crystallization.