Use Of Static Models Research Articles

Analysis of the probability of crisis events as a determinant of the financial security of food industry enterprises

Analysis of the probability of crisis events as a determinant of the financial security of food industry enterprises

What Does Dynamic Panel Analysis Tell Us About Life Satisfaction?

Static fixed effects estimation of life satisfaction often gives rise to serial correlation in the residuals, indicating omitted dynamics. Rather than correcting the standard errors, “to make them robust,” this study explores dynamic panel analysis to incorporate the otherwise omitted dynamics into the estimation of life satisfaction models. The analysis utilizes the System General Method of Moments approach to dynamic analysis. The results indicate that overall life satisfaction is largely (though not wholly) contemporaneous; correspondingly, the persistence of satisfaction from previous periods is limited. This finding is robust to a variety of different specification choices. Accordingly, the issue of omitted dynamics in a life satisfaction context is a minor one. This use of dynamic panel analysis, therefore, offers support for the ongoing use of static models (like fixed effects), even though they omit dynamics. Given the highlighted challenges of dynamic panel analysis, static fixed effects analyses will often be preferred.

Mechanisms for coordination of interests of the parties to municipal-private partnership

This research is dedicated to the use of widespread static models for coordination of common and private interests to the conditions of municipal programs. The subject of this research is the coordination of interests of the parties to municipal-private partnership projects. The goal lies in application of the static models of coordination of common and private interests to the single-stage socioeconomic processes of implementation of municipal-private partnership projects. The research methodology is structured on the use of static models of coordination of public and private interests), taking into account the utilitarian function of social well-being, the mechanism of Nash equilibrium, and the index of systemic coordination. The author carries out modeling of the coordination of interests of the parties to municipal improvement projects in the city of Novocherkassk, interprets the variants of the use of the mechanism of proportionate distribution, economic regulation and administrative control in managing the implementation of the program. The acquired results find reflection in the municipal management pertinent to the arrangement of municipal-private partnership programs and coordination of interests of the parties. The novelty of this research consists in adaptation of the abstract models of coordination of interests to the tasks of municipal management, which significantly improve the efficiency of planning municipal programs. The conclusion is made on the effectiveness of such management mechanisms for the municipal program. Recommendations are given for coordination of interests of each party to the partnership.

Defensive posture in a terrestrial salamander deflects predatory strikes irrespective of body size

Abstract A wide variety of prey use defensive postures as a means of protection from predators. Many salamanders engage in broadly similar defensive postures, which may function as a warning signal and reduce the probability of attack, or may deflect predator attacks away from vital body parts. The extent to which these strategies (i.e., aposematism and deflection) act exclusively or synergistically, however, remains unknown. We deployed clay salamanders in the field, manipulating size (small, large) and posture (resting, defensive), and documented attack rates across three predator types. Competing risks analysis revealed that attack rates were affected by model size, deployment period, and leaf litter depth at the site of deployment, whereas model posture had no significant effect. Model size and posture did not interact, indicating that defensive posture was ineffective in deterring attack irrespective of prey size. Model prey in the defensive posture received significantly more attacks on the tail irrespective of size, and the defensive posture was more effective at deflecting avian attacks compared to mammal predation. We conclude that defensive posture increases tail conspicuousness without increasing predation risk, and primarily functions to deflect attacks away from vital body parts. The efficacy of defection may be further increased by tail undulation, however our use of static models means that we cannot exclude aposematic or deimatic functions for such movements. Our results provide important support for the deflection hypothesis in explaining antipredator behavior, and thereby set the stage for additional research targeting the functionality of attack deflection in natural predator–prey encounters.

Petroleum production optimization – A static or dynamic problem?

This paper considers the upstream oil and gas domain, or more precisely the daily production optimization problem in which production engineers aim to utilize the production systems as efficiently as possible by for instance maximizing the revenue stream. This is done by adjusting control inputs like choke valves, artificial lift parameters and routing of well streams. It is well known that the daily production optimization problem is well suited for mathematical optimization. The contribution of this paper is a discussion on appropriate formulations, in particular the use of static models vs. dynamic models. We argue that many important problems can indeed be solved by repetitive use of static models while some problems, in particular related to shale gas systems, require dynamic models to capture key process characteristics. The reason for this is how reservoir dynamics interacts with the dynamics of the production system.

Continuous Learning from Human Post-Edits for Neural Machine Translation

Abstract Improving machine translation (MT) by learning from human post-edits is a powerful solution that is still unexplored in the neural machine translation (NMT) framework. Also in this scenario, effective techniques for the continuous tuning of an existing model to a stream of manual corrections would have several advantages over current batch methods. First, they would make it possible to adapt systems at run time to new users/domains; second, this would happen at a lower computational cost compared to NMT retraining from scratch or in batch mode. To attack the problem, we explore several online learning strategies to stepwise fine-tune an existing model to the incoming post-edits. Our evaluation on data from two language pairs and different target domains shows significant improvements over the use of static models.

The effect of viscous force on the prediction of muscle contractility in biohybrid cantilever-based experiments

The biohybrid cantilevers have been recently reported for high-throughput measurement of muscle contractility. In previous works, mechanical models were used to predict the contractile stress from the cantilever bending curvature. To derive those models, the cantilever bending process was considered as quasi-static and the viscous force was neglected. To ascertain the effect of the viscous force on the prediction of the muscle contractility in biohybrid cantilever-based experiments, we extend the modified Stoney’s equation to a dynamic model that takes into account both the viscous force and the inertia force. Parametric studies show that, because the viscous force hinders the movement of the cantilever, use of static models result in a system error between the calculated and true contractile stresses. When using static models, the diastolic stress will be over-estimated while the peak systolic stress will be under-estimated. The present work suggests that dynamic models can be used in biohybrid cantilever assays to calculate the muscle contractility with higher accuracy, or can be used to optimize the experimental parameters such that the error due to the use of static models is minimized.

On the Boundaries of the Shadow Economy: An Empirical Investigation

A large number of empirical studies pointed to the ongoing expansion of the shadow economy in many countries around the globe. A robust finding in these studies is the positive association between unemployment rates and the size of the unofficial sector. However, with consistent estimates of the size of the unofficial sector only available from the late 1980s, a lack of sufficient time span dictated the use of static models, allowing only a limited understanding of its temporal behavior and interdependence with other covariates. In this paper, we offer a first systematic attempt to estimate the dynamics of the shadow economy, using advanced dynamic panel techniques. Based on insights from a simple job search model of unemployment that features decreasing returns to unofficial activities and congestion effects in job searching, we conjecture a long-run equilibrium relationship between unemployment and the size of the shadow economy. Our empirical model lends strong support to this view. We find that in countries with less stringent job market regulation the long-run impact of Unemployment, the tax burden, and GDP on the shadow economy, while positive and significant, is much smaller than in heavily regulated countries Moreover, the speed of adjustment back to long-run equilibrium following temporary shocks is shown to be three times faster in countries with looser job-market regulation, compared with countries with stricter regulation. These findings have important policy implications.

Analyzing Trade Liberalization Effects in the Egg Sector Using a Dynamic Gravity Model

The objective of the paper is to explore potential changes in trade induced by a liberalization scenario when taking into account persistence in trading partners. Our approach is based on the development of a gravity model that takes into account the dynamics at the extensive margin of trade as well as the persistence effect of the intensity of trade. Our empirical contribution is on the egg sector, where the persistence in trading partners is acute. Our results indicate that the use of static models underestimate imports of table eggs by more than 50% in Canada, when compared with the use of panel dynamic specification. The dynamic specification helps explain why trade liberalizations often increase trade creation between countries that had already been trading partners, while new trading partnerships remain scarce following trade liberalization. Our results also confirm the importance of sunk cost and their negative impact on the probability of export market participation for developing countries. Those results raise questions regarding the benefit of trade liberalization for developing countries, in terms of accessing new market, if they do not benefit from special treatments.

Assessing spatio‐temporal priorities for species’ recovery in broad‐scale dynamic landscapes

Summary As threats to biodiversity from environmental change increase, assessing priorities for mitigation action becomes increasingly important. However, there have been few attempts to schedule actions across broad spatial extents that explicitly account for dynamic ecological processes and threats. We combined a dynamic occupancy model with a decision analysis framework to spatially allocate multiple recovery actions to maximize species’ probability of occupancy under threats posed by climate and land‐use change. We used the koala Phascolarctos cinereus across the Australian state of New South Wales (810 000 km2) to illustrate this approach. We considered four actions implemented on a 10 × 10 km2 grid: reduce domestic dog attacks through dog control, reduce vehicle collisions through fencing highways, protect habitat through land acquisitions and restore Eucalyptus forest. We used the occupancy model to predict ecological responses to recovery actions and simulated annealing to identify spatio‐temporal priorities for each action. We contrasted the results against priorities generated using a traditional static distribution model. To maximize the probability of koala occupancy in 50 years’ time, with an annual budget of up to AU$20 million, investment priorities were located in the eastern part of koala's range, focusing on dog control with some investment in habitat protection and restoration. With higher budgets, investment priorities shifted towards habitat protection and restoration in the western part of the range. However, priorities based on the static distribution model, which had a lower predictive accuracy than the dynamic model, were different. Regardless of budget, priorities derived from the static model were predominantly located in the western part of koala's range, focusing on highway fencing with some investment in dog control. Synthesis and applications. Our approach for integrating spatio‐temporal dynamics into conservation prioritization across broad spatial extents provides a significant advance on existing approaches based on static distribution models. The finding that the inferior static model produced different priorities to the dynamic model cautions against the use of static models for conservation planning in dynamic landscapes. Additionally, the substantial changes in priorities with budget indicate that conservation planning under dynamic landscape and climate change must carefully consider priority actions and locations relative to the conservation resources available.

Evaluation of the Use of Static and Dynamic Models to Predict Drug-Drug Interaction and Its Associated Variability: Impact on Drug Discovery and Early Development

Simcyp, a population-based simulator, is widely used for evaluating drug-drug interaction (DDI) risks in healthy and disease populations. We compare the prediction performance of Simcyp with that of mechanistic static models using different types of inhibitor concentrations, with the aim of understanding their strengths/weaknesses and recommending the optimal use of tools in drug discovery/early development. The inclusion of an additional term in static equations to consider the contribution of hepatic first pass to DDIs (AUCR(hfp)) has also been examined. A second objective was to assess Simcyp's estimation of variability associated with DDIs. The data set used for the analysis comprises 19 clinical interactions from 11 proprietary compounds. Except for gut interaction parameters, all other input data were identical for Simcyp and static models. Static equations using an unbound average steady-state systemic inhibitor concentration (I(sys)) and a fixed fraction of gut extraction and neglecting gut extraction in the case of induction interactions performed better than Simcyp (84% compared with 58% of the interactions predicted within 2-fold). Differences in the prediction outcomes between the static and dynamic models are attributable to differences in first-pass contribution to DDI. The inclusion of AUCR(hfp) in static equations leads to systematic overprediction of interaction, suggesting a limited role for hepatic first pass in determining inhibition-based DDIs for our data set. Our analysis supports the use of static models when elimination routes of the victim compound and the role of gut extraction for the victim and/or inhibitor in humans are not well defined. A fixed variability of 40% of predicted mean area under the concentration-time curve ratio is recommended.

Study of Human Orexin-1 and -2 G-Protein-Coupled Receptors with Novel and Published Antagonists by Modeling, Molecular Dynamics Simulations, and Site-Directed Mutagenesis

The class A G-protein-coupled receptors (GPCRs) Orexin-1 (OX1) and Orexin-2 (OX2) are located predominantly in the brain and are linked to a range of different physiological functions, including the control of feeding, energy metabolism, modulation of neuro-endocrine function, and regulation of the sleep-wake cycle. Site-directed mutagenesis (SDM) and domain exchange (chimera) studies have provided important insight into key features of the OX1 and OX2 binding sites. However, the precise determinants of antagonist binding and selectivity are still not fully known. In this work, we used homology modeling of OX receptors to direct further SDM studies. These SDM studies were followed by molecular dynamics (MD) simulations to rationalize the full scope of the SDM data and to explain the role of each mutated residue in the binding and selectivity of a set of OX antagonists: Almorexant (dual OX1 and OX2 antagonist), SB-674042 (OX1 selective antagonist), EMPA (OX2 selective antagonist), and others. Our primary interest was focused on transmembrane helix 3 (TM3), which is identified as being of great importance for the selectivity of OX antagonists. These studies revealed conformational differences between the TM3 helices of OX1 and OX2, resulting from differences in amino acid sequences of the OX receptors that affect key interhelical interactions formed between TM3 and neighboring TM domains. The MD simulation protocol used here, which was followed by flexible docking studies, went beyond the use of static models and allowed for a more detailed exploration of the OX structures. In this work, we have demonstrated how even small differences in the amino acid sequences of GPCRs can lead to significant differences in structure, antagonist binding affinity, and selectivity of these receptors. The MD simulations allowed refinement of the OX receptor models to a degree that was not possible with static homology modeling alone and provided a deeper rationalization of the SDM data obtained. To validate these findings and to demonstrate that they can be usefully applied to the design of novel, very selective OX antagonists, we show here two examples of antagonists designed in house: EP-109-0092 (OX1 selective) and EP-009-0513 (OX2 selective).

The irrelevance of electric power system dynamics for the loading margin to voltage collapse and its sensitivities

The loading margin to a saddle-node or fold bifurcation measures the proximity to voltage collapse blackouts of electric power transmission systems. Sensitivities of the loading margin can be used to select controls to avoid voltage collapse. We analytically justify the use of static models to compute loading margins and their sensitivities and explain how the results apply to underlying dynamic models. The relation between fold bifurcations of the static models and saddle-node bifurcations of the underlying dynamic models is clarified.

Intangible Assets and Value Creation at Brazilian Companies: An Application for the Brazilian Textile Manufacturing Sector

This paper investigates the relationship between intellectual capital and value creation in the Textile Manufacturing Sector in Brazil. Through the access of the database from the Annual Industrial Research conducted by the Brazilian Institute of Geography and Statistics, we gathered 644 observations, from 2000 to 2006, with more than 100 employees To achieve the goal of the study, we consider intellectual capital as defined by Ante Pulic including human capital and structural capital. For the analysis of business performance, we used Pulic’s VAIC index as a measure of efficiency of the employed financial and intellectual capital. Regression models were run to verify the relationship among the efficiency in the use of intellectual capital and the profitability of Brazilian companies. The gross income, calculated as before selling, general and administrative expenses, depreciation expenses, amortization and interest expenses, was used as measure of the flows of value creation and the profitability was measured by the gross income to the total assets of the companies. We tested the following hypotheses: (i) there is a positive relationship between value creation and intellectual capital, (ii) there is a positive relationship between value creation and stock of intellectual capital, (iii) there is a positive relationship between value creation and efficiency of the employed capital, (iv) there is a positive relationship between value creation and efficiency of the human capital, (v) there is a positive relationship between value creation and efficiency of the structural capital. The results of the study, obtained through panel data analysis and through the use of static models, support the hypotheses that the intellectual capital of the companies, in its flow and stock dimensions, is positively and significantly related to value creation.

Contributions of Dichotomic View of plasticity to seamlessly embed accessibility and adaptivity support in user interfaces

Recent legal changes have increased the need for developing accessible user interfaces in computer-based systems. In this sense, previously existing user interfaces are intended to be modified and new user interfaces are intended to be designed taking accessibility guidelines into account. Typically, model-based approaches have been used when developing accessible user interfaces or redefining existing ones. But the use of static models leads to the development of not dynamically adaptable user interfaces. Dynamic adaptation in accessible user interfaces is important due to the fact that interaction difficulties on people with disabilities may change through use. In this paper, we present some contributions that can be obtained from the application of the Dichotomic View of plasticity in the personalization of user interfaces. With the double perspective defined in this approach, it is intended to go further from a mere adaptation to certain user stereotypes, offering also a dynamic support to real limitations or difficulties users can encounter during the use of the UI. This goal is achieved analyzing user logs by an inference engine that dynamically infers modifications in the user interface to adjust it to varying user needs. A case study is presented in order to show how the guidelines and software support defined in the Dichotomic View of plasticity can be applied to develop a component for a particular system aimed at performing dynamic user interface adaptations with accessibility purposes. This approach includes some innovations that make it different from conventional adaptable mechanisms applied to accessibility in some important aspects.

The Use of Linear Logit Models for Dynamic Input Demand Systems

This paper demonstrates that a linear logit model, with appropriate constraints, can be used to specify a system of cost share equations that satisfy neoclassical economic conditions. Unlike many other flexible functional forms, the logistic function is particularly well suited for incorporating dynamic adjustment mechanisms. The empirical results suggest that the use of static models overstates short-run own-price elasticities and understates the corresponding long-run price effects.

Major conceptualproblems in the systems management of human factors/ergonomics research

The results or human factors/ergonomics research are not always applicable to the solution of realworld problems. Six reasons for this situation, important from a systems management perspective, are identified. Difficulties stem from future uncertainty, the use of static models, the relationship between models and data, the criteria for ‘good’ research, the hierarchical level selected for representing human performance, and the need to construct integrated models. A number of means are suggested for rectifying present deficiencies. The formal recognition of a systems management role in the guidance of human factors/ergonomics research is stressed.

Tax Changes Linked to Government Expenditure Changes and the Magnitude of Fluctuations in National Income

Governments, encouraged by their economic advisors, often change rates of taxation in line with changes in government expenditure in the belief that this will reduce the multiplier effect of government expenditures and so help to avoid fluctuations in national income. This belief is presumably based on the use of static models or unlagged dynamic models, and is correct in the context of such models. However, if there are time lags in the system, say a lag between changes in consumption and changes in personal disposable income, the appropriate model to use is a dynamic one. Section I of the present paper uses a simple dynamic model, compares results with a lagged and unlagged consumption function, and demonstrates that changing tax rates in line with government expenditure changes may prove destabilizing.1 Section II recognizes that the government sets tax rates not revenues, and performs a simple simulation for the period 1963-68 in order to examine the effect on tax revenues of setting tax rates to equate expected tax revenues (given income predictions derived from alternative expectations functions) to government expenditure.

Effect of Pion-Nucleon Final State Interaction in Backward Pion Photoproduction from Deuterium in 1 GeV Region

The effect of pion-nucleon final state interaction in the backward pion photoproduction from deuterium is calculated by using several assumptions such as the closure approixmation, the use of static model, etc. for the incident photon energy E'Y~l GeV, where the final pion-spectator system is just in the 3-3 resonance. It is shown that the ~ffect is negligible within the presently available experimental resolution. Correction to the impulse approxima­ tion calculation is estimated to be of the order of a few per cent almost independently of the detail of photoproduction amplitudes in the rather wide range of E'Y'

Further Reflections on Retail Pricing

The article Imperfect Competition in Retail Trades by Mrs. Hood and Mr. Yamey, published in the May issue of Economica, contains some interesting and important reflections on the character of retail trade. If the main purpose of the authors had been, in the light of these reflections, to question the use of static models in the analysis of competition in retail trade and if they had followed up their leading statement: It is not useful to rely upon the essentially static and long-run theory of monopolistic competition to explain the economics of retailing by an attempt to construct a dynamic model, their work would indeed have been a major contribution. The declared purpose of the authors is, however, much more limited and much more doubtful. It is to dispute the appraisal of the working of competition in retail trade contained in Henry Smith's Retail Distribution and in my Distributive Trading. What they object to is the discussion of retail trade in terms of the analysis of imperfect competition and oligopoly: The main point at issue, they write, is whether the degree and nature of the imperfections are such that it is more realistic to stress the imperfections than it is to stress the competition (particularly in its price-reducing aspect) in the study of retail markets . They hold that a dominant emphasis on imperfections is mistaken. This is the first point they wish to establish and it is critical in intent. Their second point is positive and has serious practical implications: in the absence of resale price maintenance, they argue, price competition in retail trade would be sufficiently ardent to bring about excess capacity in retailing as a consequence of the ease of entry into the distributive trades and a sign of disequilibrium but in no sense as a normal outcome of the way in which competition works at retail, which is what the theory of imperfect markets implies. The practical inference they draw is as follows It appears to