凿井水下底卸式自动卸料吊桶

吊桶是立井井筒开凿时期提升矸石和运送材料及升降人员的主要容器,吊桶的卸矸目前多采用挂钩式或座钩式卸料方式;但是随着矿井的开凿深度不断延伸,在过透水层时,由于探放水不及时或涌出水比较大,超出了井筒的排水量,或者是由于冷冻井在解冻后,井筒的井筒质量不过关,各别井壁也会发生透水事故;这就会出现淹井事故,有时淹井深度达二三百米。对于处理这种淹井事故,往往只有一个办法,那就是用沙或混凝土对井筒回填;这就需要吊桶在下到几百米下的水底自动把料卸掉,但现在矿井常用的挂钩式吊桶和座钩式吊桶已经不能满足这个需要了。     

The impact of fiscal positions on government bond yields in CEE countries

This paper investigates the influence of government debt and primary balance on long-term government bond yields in 10 Central and Eastern European (CEE) countries in the period 2000–2013. The results indicate that a one percentage point increase in the stock of government debt is associated with an increase in government bond yields of 2.7–4 basis points, while a one percentage point increase in the primary deficit to GDP ratio is associated with an increase in government bond yields of 12.9–24.3 basis points. We also find evidence of non-linearities in the debt-interest rate relationship, whereby the threshold after which the impact of debt turns from negative to positive is significantly lower than in advanced economies.     

Spatial and operational factors behind passenger yield of U.S. nonhub primary airports

Nonhub airports are an essential component in the National Plan of Integrated Airport Systems (NPIAS) of the United States in that they connect regional towns and small communities to the air transportation network. Understanding the interplay of operational and spatial factors in determining average passenger yield of nonhub airports provides airlines with valuable information for network planning and revenue management. This study examines factors contributing to the yield variation among nonhub airports in the U.S. Using ordinary least squares (OLS) based econometric models, this study captures the spatial dependence of passenger yield of nonhub airports, which tends to increase with a corresponding increase in distance to the nearest large hub airport. Nonhub airports surrounding large hub airports with higher passenger enplanements and higher average yields also have higher yields than other nonhub airports. In addition, this study finds the effect of Allegiant Airlines in lowering the average passenger yield of the nonhub airports served directly by the airline, which can be termed as ‘Allegiant Effect’. Findings of this study could provide valuable guidance for airlines to analyze network planning strategies and to identify future markets for growth and for policymakers when allocating resources to communities relying on these nonhub airports.     

Diversification strategy with random yield suppliers for a mean–variance risk-sensitive manufacturer

We consider the diversification strategy for a mean–variance risk-sensitive manufacturer with unreliable suppliers. We first analyze the linear model and find that the suppliers are selected according to the descending order of their contributed marginal expected profit, and increasing the manufacturer’s risk-averseness leads to a more even allocation of demand across the suppliers. Then, we study the general newsvendor model. By approximating the leftover inventory with a normal distribution, we establish the general properties of the active supplier set and show that the supplier selection rule is similar to that under the risk-neutral setting when the demand uncertainty is large. Moreover, we conjecture that the selection rule also applies when the demand uncertainty is low, which we verify with an extensive numerical study. Our paper makes two contributions: First, we establish the properties of the optimal diversification strategy and develop corresponding insights into the trade off between cost and reliability under the mean–variance framework. Second, we perform comparative statics on the optimal solution, with a particular emphasis on investigating how changes in the supplier’s cost or reliability affect the risk-averse manufacturer’s ordering decisions and customer service level.     

The effectiveness of the ECB’s unconventional monetary policy: Comparative evidence from crisis and non-crisis Euro-area countries

During the European financial crisis, the European Central Bank implemented a series of unconventional monetary policy measures. We argue that these programs lowered the bond yield spreads of Euro-area countries. This hypothesis is tested using pooled OLS estimations and two different datasets: monetary policy event dummies and the purchase volumes of the Securities Markets Programme (SMP). Overall, we find significantly negative effects on bond yield spreads for both datasets, leading us to accept the hypothesis. While the OMT reduces the spreads of both crisis and non-crisis countries, LTROs and the lowering of the deposit rate to 0 percent are mainly effective in non-crisis countries. The SMP lowers the spreads of crisis countries, but it has the opposite effect on non-crisis countries. This converse effect is explained by the risk that increasingly accumulates on the ECB’s balance sheet through the SMP and that way constitutes a fiscal risk for non-crisis countries. The results are confirmed by pooled OLS estimations that measure the effect of unconventional monetary policy on central government debt.     

基于GARCH族模型对中国股市波动的分析与预测

运用GARCH类模型对沪深300指数序列的波动性、收益率进行了实证研究,并且对序列做了拟合与预测,获得了不错的效果。除此,还证实了中国股市存在着显著的非对称效应。     

Measuring quality performance of cadastral survey and deeds registration work processes

When land parcel boundaries are surveyed for purposes of registration in most southern African countries, the cadastral survey records and diagrams prepared have to be examined and approved by the Surveyor General first before they can be registered in the Deeds Registries. For such records to be approved, their quality must conform to requirements stipulated in relevant acts and regulations. Where regulatory requirements are not met, the records are rejected and returned for corrections and resubmission. From a cross-organizational context, poor quality documents lodged upstream have the effect of congesting examination processes downstream as records are rejected and returned backwards due to quality failure. The paper proposes a quality performance measurement model to analyze quality performance in land administration work processes. The developed model is tested on 2 survey examination and approval sites and 3 deeds registration sites in Namibia, Zimbabwe and South Africa. Based on below expected quality results obtained at one of the sites, a root cause analysis was conducted to establish recurring and underlying causal factors upon which quality improvement strategies can be built on.     

石化产品的结构优化模型

石化产品及主要原料－原油的价格变化速度较快，这就要求企业根据市场变化及时进行产品结构调整。结合一个具有代表性的石化企业实际，运用优化方法，以原油加工量、产品收率为主要指标进行石化产品结构优化，为企业生产决策提供可靠的依据。     

证券市场成交量对收益率波动性影响的实证分析

本文根据上海证券市场上证综合指数2005年1月1日到2006年1月1日的复合收益率和日成交量。用GARCC模型描述日成交量对复合收益率的波动性影响。在GARCH模型中加入当期交易量、滞后一期的交易量，结果表明当期交易量变化率能明显削弱收益率条件方差的波动性，而滞后一期的成交量只通过对当期的成交量间接的影响复合收益率。     

On the determinants of yield spreads between mortgage pass-through and Treasury securities

Yield spreads between mortgage pass-through and U.S. Treasury securities may reflect differences in taxation, phenomena affecting relative supply and demand, and compensation for default, call, and marketability risks on mortgage instruments. Our research empirically models differences in yields between pass-throughs and comparable-maturity Treasuries. We find that interest-rate volatility and the term structure of rates, factors often cited in the mortgage pricing literature as affecting the mortgage call premium, are the primary determinants of movements in these spreads. Moreover, these effects have grown in importance in recent years as exercise of the prepayment option has increased. We also find evidence that liquidity and credit concerns affect the pricing of pass-through securities.