Replacement Investment: Optimal Economic Life Under Uncertainty

Replacement investment is essentially a regenerative optimal stopping problem; that is, the key decision concerns when to terminate the life of existing plant – and hence when to start over again. This paper examines this optimisation problem within a continuous time framework and studies the qualitative and quantitative impact of uncertainty on the timing of new investment (and the criteria that should be used for terminating the life of existing plant).     

On efficiency of the ratio estimator

Summary The exact mean square error for the ratio estimator of a finite population total based on simple random sampling without replacement is shown to have an expected value less than that of the variance of the ratio estimator based on Midzuno’s scheme, under a usual super-population model.     

广州-茂名铁路换碴施工技术

文章介绍了有关在广州-茂名铁路运用大型养路机械进行更换石碴施工的技术和经验。     

我国的M1/M2(1978-2002):长期趋势、水平与周期波动

本对我国1978—2002年的M1／M2的长期趋势、水平和周期波动进行了研究，结果表明1978—1995年，中国的M1／M2呈急剧下降的态势，但是从1996至今则基本保持平稳。另外从国别比较来看，我国属于M1／M2比较高的国家(地区)之一，这表明我国的居民和企业由于支付制度、取款成本、规避税收等原因比美、日等国家的经济主体对M1的需求高很多。除开长期走势之外，中国的M1／M2还伴随着经济活动呈周期性的波动，实证分析结果表明1996年前的经济增长率是M1／M2周期波动的Granger原因，但1996年以后则必须由名义利率、通货膨胀率和股票市场交易量的变动才能说明M1／M2的波动。     

高技术企业的权变治理、管理者更替与企业永续发展

高技术企业的治理与规范化公司的治理存在很大的差异,甚至是本质上的差异。这种差异主要来自于高技术企业的人力资本价值和团队合作价值。但从企业长期发展来看,高技术企业必须平衡权威治理和企业永续发展的关系问题。本文运用企业权力主体竞争力模型分析高技术企业控制权结构,剖析了高技术企业的“两人治理结构”现象,揭示出保持高技术企业永续发展的两大主题——权变治理和管理者更替问题。     

Comparing post-operative resource consumption following transcatheter aortic valve implantation (TAVI) and conventional aortic valve replacement in the UK

Objective:

To define the in-hospital and 6-month post-discharge resource use, following Transcatheter Aortic Valve Implantation (TAVI) and conventional Aortic Valve Replacement (AVR) surgery within a single UK hospital.

Methods:

A local service evaluation of patients undergoing TAVI or AVR between January 2011 and May 2012 captured data until 6-months post-procedure, collected from hospital records and via a General Practitioner questionnaire. The main end-points were mortality, time in ITU/HDU, hospital length of stay (LoS), discharge destination, re-admission, and post-discharge primary/secondary care resource use. Sub-group analyses were performed for AVR patients aged ≥80 (AVR?≥?80) and with EuroSCORE of ≥10 (AVR ES?≥?10) to allow more direct comparison with ‘TAVI type’ patients.

Results:

Results are given as means (standard deviation) for TAVI (n?=?51), AVR (n?=?188), AVR?≥?80 (n?=?48), and AVR ES?≥?10 (n?=?47), respectively, unless otherwise stated. Age in years was 83.0 (8.1), 71.2 (13.1), 84.1 (2.7), 79.4 (7.1); EuroSCORE was 24.7 (11.9), 8.1 (6.4), 12.0 (6.0), and 16.5 (6.6); post-operative LoS (days) was 11.5 (11.2), 10.9 (10.8), 14.3 (16.7), and 15.2 (17.7). For discharged patients, 0%, 7%, 13%, and 9% had unplanned cardiac-related re-admissions within 30-days of discharge. Time to first readmission was 74.6 (34.0), 35.0 (34.2), 20.8 (9.7), and 22.6 (14.3) days.

Limitations:

This was a single-center retrospective evaluation, not prospectively powered to confirm differences in outcomes.

Conclusions:

Despite TAVI being performed in an older, higher risk population, LoS was similar to AVR. Most strikingly there were no cardiac-related re-admissions within 30-days for TAVI and time to first re-admission was significantly longer. This evaluation suggests that TAVI is clinically appropriate and provides economic advantages in both the hospital and post-discharge setting in this high risk group. Many patients undergoing TAVI are considered unfit for surgery and, hence, TAVI offers a treatment that delivers similar results to traditional AVR without the high risk associated with surgery.     

Design and planning for green global supply chains under periodic review replenishment policies

We quantify the impact of jointly optimizing strategic network design and tactical inventory planning on the cost and CO₂ emissions of multi-echelon logistics networks. The obtained insights indicate that longer optimized replenishment cycles reduce a node’s transportation cost and CO₂ emissions but increase its inventory costs. Moreover, under a fixed replenishment cycle, a node’s service level increases when supplied by a satellite warehouse. Finally: (i) the costs of implementing optimal green network design decisions could be misleading if inventory planning is neglected, (ii) greening of supply chains could become expensive, (iii) current legislative CO₂ ton prices hardly influence logistics networks.     

Price determinants of bred heifers: Do reputations matter?

Replacement brood cows are among the most significant investments for cow-calf operations, thus crucial to profitability. Many cow-calf producers find it cost effective to purchase replacements from a reliable replacement heifer seller, though by doing so they increase risk of reproductive inefficiency due to unknown characteristics of the heifers. When important information about a product is missing to buyers, a seller can build a reputation over time that acts as signal for quality. Previous work has explored reputation effects in feeder cattle markets, but to our knowledge we are the first to explore reputation effects in bred replacement cattle markets. Using data from an annual replacement heifer sale, we analyze the values of heifer characteristics and test for premiums from reputation development. After controlling for reproductive practices, breed, and other characteristics, we find reputation does not play the role that Shapiro theorized. In this sale, the lot order is strategically chosen and may indicate bred heifer quality to buyers, replacing the need for reputation as a signal. This study highlights the importance of quality signals and regional preferences in bred replacement cattle marketing and lays the empirical groundwork for future studies to test Shapiro's theory.     

灌砂法检测路基压实度技术探讨

鉴于灌砂法在路基压实度检测中的广发应用,本文从室内和现场两个角度探讨了灌砂法相关技术问题,为公路工程建设提供参考。     

浅谈换填垫层法在软基处理中的实际运用

详细阐述了有关换土垫层法处理软弱地基的基本性能、计算设计方法,并介绍了该方法处理软弱地基的应用实例,对以后的设计有一定的参考意义。