智慧BIM乔木模型：从设计图纸到施工 现场

现有的BIM应用软件提供的乔木模型多为RPC或高 精度3D模型等3D CAD类型。这些模型着重于表达美感或进 行展示,无法反映根系情况。虽然可能包含一定附加属性,但 表达乔木生长和空间需求的功能有限。因而,冲突检查、工序 调度等BIM的优势功能无从应用。风景园林实践领域已就此问 题开始构建自己的模型库,但能够准确反映现状树木真实尺寸 体量,以及现状树木和规划树木未来空间需求的模型仍未广泛 出现。提出一种基于树冠、树干和根系构型与生长功能的实体/ 网面封装建模方法构建BIM乔木模型。模型形态通过一组参数 调整,并根据树龄和反映环境限制因子的值来反映其变化。所 包含的数据和参数数量随后期设计阶段所需的LoD(详细层级) 及专业实践的具体要求而增加。该模型可以与提供本地区内外 苗木商品信息的植物数据库连接使用。     

When prices hardly matter: Incomplete insurance contracts and markets for repair goods

This paper looks at markets characterized by the fact that the demand side is insured. In these markets, a consumer purchases a good to compensate consequences of unfavorable events, such as an accident or an illness. Insurance policies in most lines of insurance base indemnity on the insured's actual expenses, i.e., the insured would be partially or completely reimbursed when purchasing certain goods. In this setting, we discuss the interaction between insurance and repair markets by focusing, on one hand, upon the development of prices and the structure of markets with insured consumers, and, on the other hand, the resulting backlash on optimal insurance contracting. We show that even in the absence of ex post moral hazard the extension of insurance coverage will lead to an increase in prices as well as to a socially undesirable increase in the number of repair service suppliers if repair markets are imperfect.     

Noisy chaotic dynamics in commodity markets

The nonlinear testing and modeling of economic and financial time series has increased substantially in recent years, enabling us to better understand market and price behavior, risk and the formation of expectations. Such tests have also been applied to commodity market behavior, providing evidence of heteroskedasticity, chaos, long memory, cyclicity, etc. The present evaluation of futures price behavior confirms that the resulting price movements can be random, suggesting noisy chaotic behavior. Prices could thus follow a mean process that is dynamic chaotic, coupled with a variance that follows a GARCH process. Our conclusion is that models of this type could be constructed to assist in forecasting prices in the short run but not over long run time periods.First version received: June 2001/Final version received: March 2003     

International Commodity Taxation under Monopolistic Competition

We analyze non‐cooperative commodity taxation in a two‐country trade model characterized by monopolistic competition and international firm and capital mobility. In this setting, taxes in one country affect foreign welfare through the relocation of mobile firms and through changes in the rents accruing to capital owners. With consumption‐based taxation, these fiscal externalities exactly offset each other and the non‐cooperative tax equilibrium is Pareto efficient. With production‐based taxation, however, there are additional externalities on the foreign tax base and the foreign price level that lead non‐cooperative tax rates to exceed their Pareto efficient levels.     

Surplus liquidity,central bank losses and the use of reserve requirements in emerging markets

Since the turn of the millennium, stocks of foreign reserves held by central banks in many emerging markets and developing countries have exceeded currency in circulation. To steer money market rates, these central banks have been absorbing liquidity from, rather than providing it to, the banking sector in their regular monetary policy operations. When interest rates in countries with major reserve currencies are low, the yield on foreign reserves is low. A higher interest rate on liquidity‐absorbing operations may expose central banks to losses. Although a central bank is not a profit‐maximizing institution, central bank losses can undermine the independence of the central bank. Using data for a large panel of central banks, this paper provides some evidence that central banks tend to apply low‐remunerated reserve requirements when profitability is at stake.     

Aggregation of Directional Distance Functions and Industrial Efficiency

Three main objectives are pursued in this paper. First, we intend to analyze the aggregation problem of directional distance functions from a constructive viewpoint. We provide necessary and sufficient conditions concerning the structural properties of the production technology and of the nature of groups of firms. Indeed, exact additive aggregation holds for a linear technology and for a direction solely defined in the output space. Second, since these conditions are somewhat restrictive, we are interested in providing a measure for the aggregation bias through the relationship between industrial and structural technical efficiency. Finally, we show that this aggregation bias is a lower bound for industrial allocative efficiency.     

GOVERNMENT SIZE AND GROWTH: A REJOINDER

In our 2011 survey of the literature in the Journal of Economic Surveys on the effect of government size on economic growth in wealthy countries we find a relatively consistent pattern: An increase in government size by 10 percentage points is associated with a 0.5–1 percentage point lower annual growth rate. This conclusion is questioned by Colombier. In this rejoinder we present a rebuttal of Colombier's argument based on a detailed scrutiny of his own statistical evidence and regression results. Furthermore, we note that several new papers that have appeared since our original paper was published give support to our main conclusion.     

Walking and Talking Corporate Social Responsibility: Implications of Firm Size and Organizational Cost

In this paper we address two interrelated research gaps in the Corporate Social Responsibility (CSR) literature. The first results from a lack of understanding of different patterns of CSR engagement with respect to CSR talk (impression management and the creation of symbolic images and documentation) and CSR walk (substantive implementation of CSR policies, structures and procedures). Related to this, the second gap concerns limited knowledge about the influence of firm size on CSR engagement. We develop a conceptual model that explains differences in CSR talk versus walk based on organizational cost and firm size. This allows us to theorize the antecedents of what we call the large firm implementation gap (large firms tend to focus on communicating CSR symbolically but do less to implement it into their core structures and procedures) and vice versa the small firm communication gap (less active communication and more emphasis on implementation). Our model expands a new theoretical understanding of CSR engagement based on as yet underemphasized firm‐level antecedents of CSR, and opens up several new avenues for future, and in particular comparative, research.