非农化经营与农业上市公司经营绩效——理论分析与实证检验

我国农业上市公司非农化经营现象甚为严重,这一现象对农业上市公司经营绩效的影响引起了社会各界的广泛关注.农业上市公司非农化经营主要可以归纳为产业层次和企业管理层次这两方面成因.农业发展不足的现实成为我国农业上市公司非农化经营取向的最大产业背景因素.文章运用农业比较利益理论、外部性理论以及多元化经营理论,形成对农业上市公司非农化经营成因和非农化经营对绩效影响的理论分析框架.通过实证分析所得出的结论是:非农化经营从整体上减损了农业上市公司经营绩效.研究认为,政府应该着力在改善农业投资经营环境和制度创新上下功夫,才可能真正引导农业上市公司专注于农业上来;同时认为,目前农业上市公司主要应当实施农业专业化经营战略,在条件具备的情况下才实施与主业相关的多元化战略,现阶段应尽量避免非相关多元化经营.     

作业成本法在化工企业的实际应用

随着制造费用越来越复杂,其在产品中的比重也在不断增加。传统成本核算,采用按生产工时统一标准分摊制造费用的方法也逐渐显示出不足。而作业成本法以其自身的优势,解决了传统成本核算方法的不足。通过确定作业中心,分析各项费用发生的成本动因,建立作业成本库,计算产品的作业成本,明确地进行制造费用的分配,也更加准确地确定了产品的作业成本。     

北京市垃圾焚烧厂建设与运营问题分析

概述了北京市生活垃圾处理发展趋势。介绍了北京市生活垃圾焚烧厂规划、建设情况和运行现状．分析了焚烧厂规划建设与运营过程中应注意的若干问题并提出了解决问题的措施。     

New development: Fiscal reform in South Korea: looking back and moving forward

ABSTRACT

At first glance, it seems that South Korea’s three fiscal systems (mid-term expenditure framework, top-down budgeting, and performance management) function well. However, each fiscal system operates separately and they are inefficient because they follow past practices. This article explains what the problems are and how to overcome them.     

The information content of funds from operations and net income in real estate investment trusts

This study compares the information content of funds from operations (FFO) and net income (NI) in the real estate investment trust (REIT) industry. We find that models using FFO explain more of the variance in cumulative abnormal returns around earnings announcement dates than models using NI do. We also find that the information content of FFO differs across REITs of different sizes. FFO does not provide useful information to investors in the case of large REITs. Finally, we show that the gain or loss from sales of property is relevant to valuing large REITs.     

Impact of Continuous Climb Operations in ATC workload. Case-study Palma airport

This research assesses the impact of the integration of Continuous Climb operations (CCOs) on Air Traffic Control (ATC) workload. The methodology encompasses different modules: CCO, standard departing and arriving trajectories extracted from an external database, an ad-hoc algorithm for detecting and solving conflicts, and an ATC-workload model with the inclusion of CCO-task modifications. Monte Carlo simulations evaluates different combinations of these modules. Then, a sensitivity analysis is performed to evaluate two parameters: the impact of the calibration of the maximum ATC workload and the percentage increase of the CCO tasks on the ATC workload. The methodology is applied to a case study at Palma airport in Spain. Extensive numerical simulations are executed based on the integration of CCOs into the system from 0% to 100%. The integration of CCOs implies the increase of the ATC workload in the Control Tower (TWR) and the reduction in the Approach Control Centre (APP). The sensitivity analysis shows that the decrease in the increase of CCO-task workload barely affects the number of CCOs that can be operated without exceeding the workload limits. Conversely, the reduction of the ATC workload calibration allows the integration of CCOs around 50% in the case of 90% TWR calibration and up to 100% in the case of 80%.     

Study of emerging air taxi network operation using discrete-event systems simulation approach

This research focuses on understanding the air taxi operations to determine the number of air taxis required to fulfill the demand for urban air mobility in New York City (NYC). We leverage the Define, Measure, Analyze, Design, and Verify (DMADV) framework and integrate it with the systems simulation approach. Upon investigation, we find that all the parameters linearly impact the vehicle utilization, while other measures are robust, specifically with respect to the seating capacity. It is also recommended to operate initially with 70 air taxis in NYC to achieve a trade-off between customer wait time and vehicle utilization. The proposed approach can act as a recommender system for air taxi companies.     

Short-term scheduling of crude oil operations in refinery with high-fusion-point oil and two transportation pipelines

In some refineries, storage tanks are located at two different sites, one for low-fusion-point crude oil and the other for high one. Two pipelines are used to transport different oil types. Due to the constraints resulting from the high-fusion-point oil transportation, it is challenging to schedule such a system. This work studies the scheduling problem from a control-theoretic perspective. It proposes to use a hybrid Petri net method to model the system. It then finds the schedulability conditions by analysing the dynamic behaviour of the net model. Next, it proposes an efficient scheduling method to minimize the cost of high-fusion-point oil transportation. Finally, it gives a complex industrial case study to show its application.     

Evaluating information diffusion speed and its determinants in social media networks during humanitarian crises

The rapid diffusion of information is critical to combat the extreme levels of uncertainty and complexity that surround disaster relief operations. As a means of gathering and sharing information, humanitarian organizations are becoming increasingly reliant on social media platforms based on the Internet. In this paper, we present a field study that examines how effectively information diffuses through social media networks embedded in these platforms. Using a large dataset from Twitter during Hurricane Sandy, we first applied Information Diffusion Theory to characterize diffusion rates. Then, we empirically examined the impact of key elements on information propagation rates on social media. Our results revealed that internal diffusion through social media networks advances at a significantly higher speed than information in these networks coming from external sources. This finding is important because it suggests that social media networks are effective at passing information along during humanitarian crises that require urgent information diffusion. Our results also indicate that dissemination rates depend on the influence of those who originate the information. Moreover, they suggest that information posted earlier during a disaster exhibits a significantly higher speed of diffusion than information that is introduced later during more eventful stages in the disaster. This is because, over time, participation in the diffusion of information declines as more and more communications compete for attention among users.     

Global engineering services: Shedding light on network capabilities

This paper addresses the operations challenges of effectively managing professional services on a global scale. The specific context for the study is professional engineering services and particularly those that are delivered globally – global engineering services (GES). Estimates suggest that the market for GES was around US$930 billion in 2012, rising to US$1.4 trillion by 2020 (ISG, 2013). Yet this influential sector receives scant attention in the operations management literature. The paper draws on six case studies to explore the operations management challenges of delivering GES. In doing so the paper introduces the concept of network capabilities for GES, highlighting the centrality that: (i) network resources – accessing and deploying dispersed resources, (ii) network coordination – coordinating and integrating network activities, and (iii) network learning – collective learning and knowledge management, all play in enabling the successful operational management of GES.