600MW机组T91焊口裂纹分析

通过对600MW发电机组三级过热器SA213-T91管子焊接热影响区出现的裂纹进行宏观及微观分析,阐述了T91的组织和机械性能、使用条件及焊接裂纹的产生机理,提出T91小管在焊接、热处理及使用中应注意的几个问题,充分了解了它的优、缺点。     

Dynamic pairs trading using the stochastic control approach

We propose a model for analyzing dynamic pairs trading strategies using the stochastic control approach. The model is explored in an optimal portfolio setting, where the portfolio consists of a bank account and two co-integrated stocks and the objective is to maximize for a fixed time horizon, the expected terminal utility of wealth. For the exponential utility function, we reduce the problem to a linear parabolic partial differential equation which can be solved in closed form. In particular, we exhibit the optimal positions in the two stocks.     

Optimality conditions¶and bubbles in sequential economies¶and bounded relative risk-aversion

We provide specific qualifications in order that Kuhn–Tucker type Euler equations and transversality conditions at infinity hold in stochastic equilibrium models with heterogeneous agents and where assets are traded in sequential markets. It is not assumed that uncertainty is modeled as an event-tree structure or that preferences are necessarily bounded. We also describe an important class of preferences based on bounded relative risk aversion which yields relevant simplifications. Our results are used to establish conditions that rule out asset pricing bubbles. Specific examples of economies with bubbles are also discussed. Received: 28 January 2002 / Accepted: 19 July 2002 We are grateful to the editor and an anonymous referee for their valuable comments. This research was partially supported by MURST (Italy), National Group on “Nonlinear Dynamics and Stochastic Models in Economics and Finance”.     

An elementary core equivalence theorem¶in a countable economy

We consider an infinite exchange economy with countably many traders, which can be regarded as a natural extension of finite exchange economies to an infinite one. In our countable economy the core defined in the traditional manner would be empty. To avoid this unwanted situation we have to strengthen the notion of “improves upon”. We will achieve this based on the idea that forming coalitions involve costs. Received: 23 August 2000 / Accepted: 12 April 2002 I am very grateful to István Dancs, Péter Medvegyev, Miklós Pintér, Csaba Sándor, András Simonovits, László Szili, Péter Tallos and the anonymous referees for comments and suggestions. Parts of this research were done during the author's Bolyai János Research Fellowship provided by the Hungarian Academy of Sciences (MTA). Of course, all errors remain the author's responsibility.     

Single factor models with Markovian spot interest rate: an analytical treatment

In the spirit of the Heath–Jarrow–Morton methodology, we provide an analytical characterization of bond prices within the context of single factor term structure models in which the spot rate follows a Markov process and the volatility structure of zero coupon bond returns is stochastic. Also, a perturbative analysis of the extended Cox–Ingersoll–Ross model is proposed. Received: 7 February 2001 / Accepted: 8 June 2002     

Bargaining over an uncertain outcome:¶the role of beliefs

We study the Nash bargaining solution of a problem in which two agents bargain over an uncertain outcome. Under the assumptions of risk neutrality and of constant absolute risk aversion, we study the way that the solution varies, ex ante, when we vary the beliefs of one agent. Changing an agent's beliefs in a way that makes them “more distant” from the other agent's beliefs makes the second agent better off. Received: 10 May 2001 / Accepted: 22 August 2001     

Utility maximization under a shortfall risk constraint

The article analyzes optimal portfolio choice of utility maximizing agents in a general continuous-time financial market model under a joint budget and downside risk constraint. The risk constraint is given in terms of a class of convex risk measures. We do not impose any specific assumptions on the price processes of the underlying assets. We analyze under which circumstances the risk constraint is binding. We provide a closed-form solution to the optimization problem in a general semimartingale framework. For a complete market, the wealth maximization problem is equivalent to a dynamic portfolio optimization problem.     

General equilibrium in CLO markets

We address a two-period equilibrium model with securitization of collateral-backed promises. Borrowers may suffer extra-economic default penalties and debts are pooled into collateralized loans obligations (CLO), allowing different seniority levels among tranches in a same CLO.     

Are CEOs expected utility maximizers?

Are individuals expected utility maximizers? This question represents much more than academic curiosity. In a normative sense, at stake are the fundamental underpinnings of the bulk of the last half-century’s models of choice under uncertainty. From a positive perspective, the ubiquitous use of benefit-cost analysis across government agencies renders the expected utility maximization paradigm literally the only game in town. In this study, we advance the literature by exploring CEO’s preferences over small probability, high loss lotteries. Using undergraduate students as our experimental control group, we find that both our CEO and student subject pools exhibit frequent and large departures from expected utility theory. In addition, as the extreme payoffs become more likely CEOs exhibit greater aversion to risk. Our results suggest that use of the expected utility paradigm in decision making substantially underestimates society’s willingness to pay to reduce risk in small probability, high loss events.     

Estimating a Parsimonious Model of Inequality Aversion in Stackelberg Duopoly Experiments*

In the Stackelberg duopoly experiments in Huck et al. (2001) , nearly half of the followers’ behaviours are inconsistent with conventional prediction. We use a test in which the conventional self‐interested model is nested as a special case of an inequality aversion model. Maximum likelihood methods applied to the Huck et al. (2001) data set reject the self‐interested model. We find that almost 40% of the players have disadvantageous inequality aversion that is statistically different from zero and economically significant, but advantageous inequality aversion is relatively unimportant. These estimates provide support for a more parsimonious model with no advantageous inequality aversion.     

Stochastic utility theorem

This paper analyzes individual decision making. It is assumed that an individual does not have a preference relation on the set of lotteries. Instead, the primitive of choice is a choice probability that captures the likelihood of one lottery being chosen over the other. Choice probabilities have a stochastic utility representation if they can be written as a non-decreasing function of the difference in expected utilities of the lotteries. Choice probabilities admit a stochastic utility representation if and only if they are complete, strongly transitive, continuous, independent of common consequences and interchangeable. Axioms of stochastic utility are consistent with systematic violations of betweenness and a common ratio effect but not with a common consequence effect. Special cases of stochastic utility include the Fechner model of random errors, Luce choice model and a tremble model of [Harless, D., Camerer, C., 1994. The predictive utility of generalized expected utility theories. Econometrica 62, 1251–1289].     

Judgment aggregators and Boolean algebra homomorphisms

The theory of Boolean algebras can be fruitfully applied to judgment aggregation: assuming universality, systematicity and a sufficiently rich agenda, there is a correspondence between (i) non-trivial deductively closed judgment aggregators and (ii) Boolean algebra homomorphisms defined on the power-set algebra of the electorate. Furthermore, there is a correspondence between (i) consistent complete judgment aggregators and (ii) 2-valued Boolean algebra homomorphisms defined on the power-set algebra of the electorate.     

Inter-temporal preference for flexibility and risky choice

We derive an inter-temporal theory of choice, in the spirit of Kreps and Porteus [Kreps, D.M., Porteus, E.L., 1978. Temporal resolution of uncertainty and dynamic choice theory. Econometrica 46, 185–200], where decision makers have incomplete preferences. This can be used to model indecisiveness as well as unforeseen contingencies. The key to our approach is a time consistency condition and therefore the normative connection between ex-ante and ex-post choice. The time consistency condition enables a representation that is a straight forward extension of recursive utility with the exception that it features an inter-temporal ‘utility for flexibility’.     

Precautionary and Entrepreneurial Savings: New Evidence from German Households*

Various studies interpret the positive correlation between income risk and wealth as evidence of significant precautionary savings. However, these high estimates emerge from pooling non‐entrepreneurs and entrepreneurs, without controlling for heterogeneity. This article provides evidence for Germany based on representative panel data that includes private wealth balance sheets. Entrepreneurs, who face high income risk, hold more wealth than employees, but this tendency is not because of precautionary motives. Instead, they appear to save more for their old age, because they are usually not covered by statutory pension insurance. The analysis accounts for endogeneity in entrepreneurial choice and heterogeneous risk attitudes.     

Can we identify Walrasian allocations?

Abstract. We consider a discrete time, pure exchange infinite horizon economy with consumers and consumption goods per period. Within the framework of decentralized mechanisms, we show that for any given consumption trade at any period of time, say at time one, the consumers will need in general an infinite dimensional (informational) space to identify such a trade as an intertemporal Walrasian one. However, we show a set of environments where the Walrasian trades at each period of time can be achieved as the equilibrium trades of a sequence of decentralized competitive mechanisms, using only both current prices and quantities to coordinate decisions. Received: 1 December 1999 / Accepted: 31 October 2000     

Price uncertainty, saving, and welfare

We analyze how commodity price uncertainty affects saving behavior and welfare in a dynamic model with multiple commodities, portfolio hedging, and a preference structure that disentangles ordinal preferences, attitudes towards risk, and attitudes towards intertemporal substitution. We show that the effect of price uncertainty on savings boils down to knowing (1) hf degree of resistance to intertemporal substitution and (2) the effect that uncertainty has on the certainty-equivalent real interest rate. We also show that, if the certainty-equivalent real interest rate is lower with uncertainty, consumers' welfare is also lower.     

‘Stochastically more risk averse:’ A contextual theory of stochastic discrete choice under risk

Microeconometric treatments of discrete choice under risk are typically homoscedastic latent variable models. Specifically, choice probabilities are given by preference functional differences (given by expected utility, rank-dependent utility, etc.) embedded in cumulative distribution functions. This approach has a problem: Estimated utility function parameters meant to represent agents’ degree of risk aversion in the sense of Pratt (1964) do not imply a suggested “stochastically more risk averse” relation within such models. A new heteroscedastic model called “contextual utility” remedies this, and estimates in one data set suggest it explains (and especially predicts) as well as or better than other stochastic models.     

A family production overlapping generations economy

This paper provides a theoretical analysis of an overlapping generations economy in which production decisions and input–output allocations are all carried out at the family level. I consider a single class of output allocation schemes and various degrees of knowledge about the production technology. Under complete knowledge, I show that a family organizational structure in which everyone receives his marginal contribution to output, invests less in physical capital than under a perfectly competitive equilibrium environment. Under incomplete knowledge, I analyze and compare how beliefs about the input–output relationship affect the physical capital accumulation dynamics and the long-run standards of living.     

House Price Shocks,Windfall Gains and Hours of Work: British Evidence*

Do workers adjust hours of work in response to capital gains and losses? This paper investigates this question using British panel data on individual employees from 1992 to 2001. It investigates hours of work adjustments to two sources of capital gain: financial windfalls and real housing wealth gains. Significant reductions in hours are found for both men and women in response, in particular, to housing gains. Men appear to increase hours in response to real housing losses, whereas women reduce hours in response to real housing gains. Evidence on hours of work preferences suggests that observed adjustments are only partial responses.     

Consumption and labor supply

We present a new econometric model of aggregate demand and labor supply for the United States. We also analyze the allocation full wealth among time periods for households distinguished by a variety of demographic characteristics. The model is estimated using micro-level data from the Consumer Expenditure Surveys supplemented with price information obtained from the Consumer Price Index. An important feature of our approach is that aggregate demands and labor supply can be represented in closed form while accounting for the substantial heterogeneity in behavior that is found in household-level data. As a result, we are able to explain the patterns of aggregate demand and labor supply in the data despite using a parametrically parsimonious specification.