Theoretical Deficiencies Research Articles

Augmenting defense-in-depth with the concepts of observability and diagnosability from Control Theory and Discrete Event Systems

Defense-in-depth is a fundamental principle/strategy for achieving system safety. First conceptualized within the nuclear industry, defense-in-depth is the basis for risk-informed decisions by the U.S. Nuclear Regulatory Commission, and is recognized under various names in other industries (e.g., layers of protection in the Chemical industry). Accidents typically result from the absence or breach of defenses or violation of safety constraints. Defense-in-depth is realized by a diversity of safety barriers and a network of redundancies. However, this same redundancy and the intrinsic nature of defense-in-depth – the multiple lines of defense or “protective layers” along a potential accident sequence – may enhance mechanisms concealing the occurrence of incidents, or that the system has transitioned to a hazardous state (accident pathogens) and that an accident is closer to being released. Consequently, the ability to safely operate the system may be hampered and the efficiency of defense-in-depth may be degraded or worse may backfire. Several accidents reports identified hidden failures or degraded observability of accidents pathogens as major contributing factors. In this work, we begin to address this potential theoretical deficiency in defense-in-depth by bringing concepts from Control Theory and Discrete Event Systems to bear on issues of system safety and accident prevention. We introduce the concepts of controllability, observability, and diagnosability, and frame the current understanding of system safety as a “control problem” handled by defense-in-depth and safety barriers (or safety constraints). Observability and diagnosability are information-theoretic concepts, and they provide important complements to the energy model of accident causation from which the defense-in-depth principle derives. We formulate a new safety-diagnosability principle for supporting accident prevention, and propose that defense-in-depth be augmented with this principle, without which defense-in-depth can degenerate into a defense-blind safety strategy. Finally, we provide a detailed discussion and illustrative modeling of the sequence of events that lead to the BP Texas City Refinery accident in 2005 and emphasize how a safety-diagnosable architecture of the refinery could have supported the prevention of this accident or mitigated its consequences. We hope the theoretical concepts here introduced and the safety-diagnosability principle become useful additions to the intellectual toolkit of risk analysts and safety professionals and stimulate further interaction/collaboration between the control and safety communities.

Understanding the Success of Perfect Information Monte Carlo Sampling in Game Tree Search

Perfect Information Monte Carlo (PIMC) search is a practical technique for playing imperfect information games that are too large to be optimally solved. Although PIMC search has been criticized in the past for its theoretical deficiencies, in practice it has often produced strong results in a variety of domains. In this paper, we set out to resolve this discrepancy. The contributions of the paper are twofold. First, we use synthetic game trees to identify game properties that result in strong or weak performance for PIMC search as compared to an optimal player. Second, we show how these properties can be detected in real games, and demonstrate that they do indeed appear to be good predictors of the strength of PIMC search. Thus, using the tools established in this paper, it should be possible to decide a priori whether PIMC search will be an effective approach to new and unexplored games.

Testing non‐nested demand relations: linear expenditure system versus indirect addilog*

In applied economic research computable general equilibrium (CGE) models in which the behavior of economic agents are modeled, are widely used. In many CGE models, the linear expenditure system (LES) is used to model the behavior of the household sector. The disadvantage of LES is that the Engel curves, describing the relationship between expenditure on a certain commodity and total expenditure, are straight lines. Moreover, the LES does not allow for the existence of inferior commodities, elastic demand and gross substitution. An alternative model for the household block is the indirect addilog system (IAS), which is as simple to implement as LES, but which does not suffer from these theoretical deficiencies. In this paper, we test the LES specification against the IAS specification in case one disposes of a budget survey. Consequently, IAS provides a theoretically richer description of household behavior than LES, while it is also easy to implement.It is not possible to use a standard likelihood ratio test as both models are not nested. We propose to use the likelihood ratio test for non‐nested hypotheses due to Vuong [(1989), Likelihood ratio tests for model selection and non‐nested hypotheses, Econometrica 57, 307–333.] or, alternatively, the distribution‐free test due to Clarke [(2007), A simple distribution‐free test for nonnested model selection, Political Analysis 15, 347–363.]. We apply both tests to the Palestinian Expenditure and Consumption Survey [PECS (2005), Palestinian Central Bureau of Statistics, Ramallah, Palestine.] and find that there is overwhelming evidence that the IAS specification is to be preferred to the LES specification.

Behavior of cylindrical liquid jets evolving in a transverse acoustic field

This paper presents a theoretical and an experimental investigation of low-velocity cylindrical liquid jets submitted to transverse planar acoustic waves. For this purpose, the behavior of a liquid jet traversing the section of a Kundt tube was examined. Experiments reported that the liquid jet could be either deviated from its trajectory or deformed as a succession of lobes oriented in space and whose length and width depend on the jet acoustic environment. Furthermore, for a sufficient acoustic velocity, the jet deformation increases in such proportion that a premature and vivid atomization mechanism disintegrates the liquid flow. Theoretical models are proposed to understand these behaviors. The first one calls out for acoustic radiation pressure to explain the jet deviation. The second one consists in a modal analysis of the vibrations of a jet when submitted to a transverse stationary acoustic field. As a first approach, a simplified two-dimensional model is proposed. This model reports that a sudden exposition of the jet to an acoustic field triggers two jet eigenmodes. One of them induces jet deformations that were not experimentally observed. This part of the solution emerges due to theoretical deficiencies. However, the second mode reproduces the lobe formation and leads to atomization criteria in good agreement with the experimental results. The paper ends with an extension of the mathematical development in three dimensions in order to provide a basis to a more consistent model.

Medicines concordance in clinical practice

Medicines concordance in clinical practice

Developing a process re-engineering-oriented organizational change exploratory simulation system (PROCESS)

In the past two decades, business process re-engineering (BPR) and organizational restructuring (OR) have been two of the most popular approaches to improving the efficiency and the effectiveness of an organization. However, a review of the relevant literature reveals that the two approaches have been studied in isolation. The theoretical gap in academic research is also reflected in practice. The present paper therefore proposes a customer-oriented and process-focused two-stage framework, entitled the ‘process re-engineering-oriented organizational change exploratory simulation system’ (‘PROCESS’), to address these theoretical deficiencies. Two key concepts are introduced in this two-stage framework. The first is the ‘process module’ (PM), which indicates a set of common sequential activities that can be grouped as a subunit of a business process. The second is the ‘macro-process’ (MP), which indicates that a set of business processes have similar characteristics or functions. The two concepts serve as ‘stepping stones’ between BPR and OR. Based on these two concepts, the decision rules and the mathematical/simulation model can be developed under this two-stage framework. The paper then presents a case study to demonstrate the effectiveness of the ‘PROCESS’.

Patronage-Preserving Federalism? Legislative Malapportionment and Subnational Fiscal Policies in Argentina

This paper builds on institutional analysis to generate new conclusions about the economic viability of federalism. It does so by suggesting that Weingast´s seminal model of marketpreserving federalism falls short of accounting for the poor fiscal performance of multitiered systems in the developing world. This theoretical deficiency stems to a large extent from the insufficient attention paid by this model to the institutional complexity of federal systems, particularly the public policy effects of legislative malapportionment. Subsequent to an analytical discussion of the potential public spending and distributive politics distortions resulting from overrepresentation, we offer preliminary empirical evidence from Argentina, a federation exhibiting one of the most decentralized fiscal systems in the world and severe imbalances in the territorial distribution of legislative and economic resources. The findings show not only that said imbalances lead to sub‐optimal fiscal results but also that they have a mutually‐reinforcing relationship with regionalized patronage. Der Autor dieses Beitrages fragt mit institutionenanalytischem Zugriff nach den okonomischen Implikationen foderalistischer Systeme. Das grundlegende Modell des „markterhaltenden Foderalismus“ (nach Weingart) bietet keine adaquate Erklarung fur die schlechte fiskalische Performance mehrstufiger Systeme in Entwicklungslandern. Dieses theoretische Defizit resultiert weitgehend aus der ungenugenden Aufmerksamkeit, die dieses Modell der institutionellen Komplexitat foderaler Systeme widmet, insbesondere den Auswirkungen legislativer Uberreprasentation fur die offentliche Politikgestaltung. Nach einer Diskussion der potentiellen Verzerrungen in der offentlichen Ausgaben‐ und Verteilungspolitik als Folge ungleicher legislativer Reprasentation folgt eine empirische Analyse des Falls Argentinien. Argentinien ist ein foderaler Staat mit einem der am weitesten dezentralisierten Fiskalsysteme weltweit und gravierenden Ungleichgewichten in der Verteilung legislativer und okonomischer Ressourcen. Die Ergebnisse zeigen, dass die genannten Ungleichgewichte nicht nur zu suboptimalen fiskalischen Resultaten fuhren, sondern auch ein sich wechselseitig verstarkendes Verhaltnis mit regionalisierten Patronagebeziehungen aufweisen.

Toward a formal research framework for ontological analyses

Ontological analyses have been used in numerous publications to compare existing modelling grammars with an ontology. However, a sound theoretical research framework is still missing. Consequently, working with the results of such ontological analyses is theoretically questionable. Therefore, the aim of this paper is threefold. Firstly, we want to contribute to such a theoretical research framework by formalising the ontological analyses approach as sets of mathematical functions between ontological and modelling grammar constructs. Secondly, on this basis, we derive four formal requirements each ontological analyses must comply with. Thirdly, we analyse whether current state of the art ontological analyses comply with our findings. While the formalisation demonstrates the strengths of the ontological analysis approach we conclude that current analyses have theoretical deficiencies, which lead to serious limitations in their application. Lastly, we demonstrate the usefulness of our formal framework by describing a new application. This application uses two different ontological analyses as input and produces mappings between the modelling grammars used in these analyses as output.

Toward an Identity Theory of International Organizations

Despite the contemporary prominence of international organizations (IOs), their ontological status largely remains nebulous. Traditional international relations (IR) theories tend to regard an IO mainly as an instrument created to serve powerful states’ interests (neorealism) or to facilitate interstate cooperation on certain regulatory areas (neoliberal institutionalism). Therefore, those theories hardly offer a satisfactory explanation of a distinctive mode of IOs’ identity-forming process, in which a particular IO, as a separate and autonomous organic entity, grows, evolves and eventually makes sense of its own existence. This Article offers a novel perspective that attempts to overcome the aforementioned theoretical deficiency. Drawing on the identity theory in psychology, this new perspective captures an IO’s internal normative development in which one can witness a dynamic process of identity formation. The Article argues that based on its autonomy qua organization, and not merely as an instrument of states, an IO forms its unique legal identity as it experiences a normative crisis in a similar way in which a human individual does. An IO discovers its genuine identity only after it achieves a necessary level of institutional maturity as a result of incessant legal interactions and communications with its environment. The Article tests this new framework by applying it to the World Trade Organization (WTO).

Indicators for Measuring Fiscal Sustainability: A Comparison of the OECD Method and Generational Accounting

Based on an empirical application for Germany, we compare two methods of measuring fiscal sustainability: the generational-accounting approach and the OECD method. In a first step, we show that the two methods can be transformed into one another. Hence, the indicators of generational accounting can be used for the OECD method and vice versa, thus enlarging the set of sustainability indicators for both methods. In a second step, we discuss these indicators with respect to their theoretical deficiencies, tangibility, and sensitivity. Finally, we come to the conclusion that a combination of indicators stemming from both approaches can give a more general and understandable description of fiscal sustainability and satisfy a strictly defined condition of sustainability at the same time.

A theoretical analysis of the force models in discrete element method

This paper presents an investigation of the equilibrium, stability and pure rolling problems of a sphere moving on a flat plane with special reference to a few force models which are commonly used in the discrete element method (DEM) and here categorized into two types: with and without rolling friction. It is obtained that according to the models without rolling friction, the set of equilibrium states of the system is not asymptotically stable, which does not agree with the fact that the sphere with small initial tangential velocity, angular velocity and tangential displacement should eventually stop. The models also display that the sphere can roll on the plane without sliding only when both the tangential force and torque acting on the sphere are zero, which is not reasonable for a viscoelastic sphere moving on a hard plane. On the other hand, the models with rolling friction cannot describe the pure rolling motion of the sphere with any material properties. The results highlight the theoretical deficiency associated with the force models in DEM. Based on the findings, modified models are proposed to overcome the above problems.

Numerical validation of dispersion relations using a cylindrical wave for 2D FDTD methods

AbstractThe numerical dispersion of a proposed new FDTD scheme is often evaluated and compared with that of well‐established FDTD methods. Because there may be a theoretical deficiency in the dispersion analysis, numerical experimentation is often used to validate the dispersion relation. This paper describes the “matching method” for validation using a cylindrical wave in the two‐dimensional (2D) case. The matching method is demonstrated by evaluating the numerical dispersion of Yee's FDTD and ADI‐FDTD. The result is compared with the analytical numerical dispersion relation, and excellent agreement is obtained. The difference between the theoretical value for the numerical dispersion and that from numerical experiments using the matching method is 10−5 for Yee's FDTD and 10−4–10−5 for ADI‐FDTD. The numerical velocity obtained from the matching method satisfies the theoretical dispersion relation with residual errors to the order of 10−6. Such accuracy is sufficient to conclude that a numerical dispersion relation is correct. Although the matching method uses a cylindrical wave to test the numerical dispersion relation, the cylindrical wave is not a solution of the difference equations, thus it cannot be used to derive a theoretical dispersion relation. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 138–142, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20400

Combined Quantum Chemical/RRKM-ME Computational Study of the Phenyl + Ethylene, Vinyl + Benzene, and H + Styrene Reactions

Reactions of phenyl radicals with ethylene (R1), vinyl radicals with benzene (R2), and H-atoms with styrene (R3) are important prototype processes pertinent to the formation and degradation of aromatic hydrocarbons in high-temperature environments. Detailed mechanisms for these reactions are elucidated with the help of quantum chemical calculations at the G2M level of theory. Reactions R1−R3 initially produce chemically activated intermediates interconnected by isomerization pathways on the extended [C8H9] potential energy surface. All kinetically important transformations of these isomeric C8H9 radicals are explicitly characterized and utilized in the construction of multichannel kinetic models for reactions R1−R3. Accurate thermochemistry is evaluated for the key intermediates from detailed conformational and isodesmic analyses. An examination of the G2M energetic parameters for reactions R1−R3 and for briefly revisited C6H5 + C2H2 and C6H6 + H addition reactions reveals common theoretical deficiencies ...

Middle and upper thermospheric odd nitrogen: 1. A new analysis of rocket data

We evaluate the NRLMSISE‐00 model for calculations of odd nitrogen (NO, N(4S)) in the middle to upper thermosphere (z = 140–250 km). NRLMSISE‐00 incorporates new data on O2 that improves the agreement between odd nitrogen models and data significantly. In particular, the photochemical calculation that uses NRLMSISE‐00 predicts a NO solar cycle variation that is significantly less than previous calculations and that agrees well with the NO observations. This agreement is consistent with the inference from FUV solar occultation data that the O2 abundance above 140 km varies weakly with solar activity and that the O2 vertical profile at solar maximum is sensitive to other factors besides molecular diffusion. Residual discrepancies remain with the comparison of calculated to observed N(4S), which may be due to a combination of theoretical deficiencies and uncertainties in the observations.

Chaos, Uncertainty, and Policy Choice: Utilizing the Adaptive Model

This paper explores new policy models adaptable to a new policy environment, ‘Age of Chaos,’ characterized by uncertainty, complexity and nonlinear relations. This article identifies the limits of existing policy choice models, presents an adaptive model as a new explanatory tool that suits situations of extreme uncertainty, complexity and chaos. It addresses a series of discussions on contents, features and utility. An adaptive model as a decision-making principle in which complex factors seek norms in positive sum amidst dynamic uncertainty in a policy environment does not only complement existing theoretical deficiency current policy-making models, but also reaches an explanation surpassing them. It also has the features of a self-access study system settling, managing inherent policy contradictions and tracing goals in the midst of extreme disorder and chaos through an infinite self-evolution process. Ultimately, it can develop into a policy choice model with the highest adaptability. In the uncertain, dynamic and non-linear chaotic environments of today, this model can control disturbance in policy outcomes and deal with interference by unpredictable opportunistic factors. It can inspire officers in charge of policy implementation, and force bureaucratic government organizations into self-organization and change.

Researching social and ethnic identity

This paper focuses on the relationship between the conceptual and methodological problems in the study of social and ethnic identity. The author argues that the theoretical and conceptual deficiencies in defining and understanding the notions of “identity” and “ethnic identity” are reflected in the quality and type of research strategies used to asses empirical claims to ethnic identity. The first part of the paper critically reviews and analyses the use of the concepts “identity” and “ethnic identity” in social science and the humanities. The author focuses in particular on the conceptual history and geography of “identity” stressing its cultural and historical exclusivity. The second part of the paper assesses how these conceptual, historical and cultural problems affect methodological and research strategies in the study of ethnic identity.

불균형 휨모멘트를 받는 플랫 플레이트-기둥 외부접합부의 강도

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 해석 프로그램3. 변수연구4. 외부접합부의 강도산정5. 외부접합부 강도산정모델의 검증 및 근사법6. 결론참고문헌요약

VaR and expected shortfall in portfolios of dependent credit risks: Conceptual and practical insights

In the first part of this paper we address the non-coherence of value-at-risk (VaR) as a risk measure in the context of portfolio credit risk, and highlight some problems which follow from this theoretical deficiency. In particular, a realistic demonstration of the non-subadditivity of VaR is given and the possibly nonsensical consequences of VaR-based portfolio optimisation are shown. The second part of the paper discusses VaR and expected shortfall estimation for large balanced credit portfolios. All standard industry models (Creditmetrics, KMV, CreditRisk +) are presented as Bernoulli mixture models to facilitate their direct comparison. For homogeneous groups it is shown that measures of tail risk for the loss distribution may be approximated in large portfolios by analysing the tail of the mixture distribution in the Bernoulli representation. An example is given showing that, for portfolios of lower quality, choice of model has some impact on measures of extreme risk.

The developmental roots of consciousness and emotional experience

Charles Darwin is generally credited with having formulated the first systematic attempt to explain the evolutionary origins and function of the expression of emotions in animals and humans. His ingenious theory, however, was burdened with popular misconceptions about human phylogenetic heritage and bore the philosophical and theoretical deficiencies of the brain science of his era that his successors strove to overcome. In their attempts to rectify Darwin’s errors, William James, James Mark Baldwin and John Dewey each made important contributions to a theory of emotion, which attempted to put it on a more secure philosophical and scientific footing. My contention is that Dewey and his collaborator, infant experimentalist Myrtle McGraw, succeeded where their contemporaries failed. They pointed the way out of the morass of recapitulationism, and showed how a developmental theory of consciousness, mind and emotion could be formulated that avoided the epistemological and ontological pitfalls of Darwin’s theory. Drawing on an extensive body of research from contemporary experimental studies of infant development, this essay attempts to put the questions raised by these historical figures about the structure, function and value of emotions in a theoretical framework. A developmental theory is proposed about the complex, interacting neurobiological and neurobehavioral factors that contribute to human emotional development. This theory identifies the possible relationships among emotions, consciousness and mind and how their co-development influences the capacity of young children to form moral judgments.

Developments of the payback method

In spite of its theoretical deficiencies, the payback (PB) method is commonly used for appraisals of capital investments in companies. Sometimes the method is used when aspects such as liquidity and project time risk are focused, but it is also commonly used in pure profit evaluations as a single criterion. The two main deficiencies of the PB method are that it does not measure the time value of money in a correct manner and that it ignores cash flows after the payback period (PP). These deficiencies can be reduced if the maximum acceptable PP is chosen in a somewhat more sophisticated way. In practice the maximum acceptable PP is often chosen as a fixed value, e.g., three years. In some cases the limit value of the PP has been related to the economic life of the investment, e.g., a PP shorter than half the economic life. If these two rules of thumb are combined, a more theoretically correct evaluation of investments can be achieved. Such a combined PB method is based on the assumption of constant yearly cash flows. However, the method can be developed to handle cases with varying cash flows, but then some of its simplicity is lost. Due to the fact that the decision situations in the evaluation of capital investments typically are uncertain concerning the time pattern and the duration of the cash flows, this can justify the use of a simple but more robust PB method even if there would be time for more advanced analyses.