The greenhouse gas footprints of China's food production and consumption (1987-2017).

As China urbanized and its economy grew rapidly, its food production and consumption patterns changed dramatically over the past three decades. With this in mind, we evaluate how the nation's greenhouse gas (GHG) emissions related to food production and consumption altered from 1987 to 2017. We further explore key factors that affect GHG emission changes from agricultural production and household diet perspectives. We find that the GHG emissions from China's food production rose 51 percent, while that from food consumption rose 64 percent. The rise in GHG footprint of China's food production was largely caused by the increasing material- and energy-intensive food production system. Agricultural modernization was a main cause of the rise in GHGs, as China was late to the game in improving agricultural productivity. But a more meat-intensive diet accompanied by a general rise in households' use of processed food also helped to drive these transformations. China's growing appetite for meat not only intensified GHG mitigation pressures domestically, but also abroad, as Chinese households began to demand greater variety that was satisfied via imports. Indeed, GHG emissions embodied in imported meats rose over eleven-fold from 2007 to 2017. Through this study, we highlight the importance of future policy-making focused on a more sustainable food system in China to benefit the world's environment, health, and climate.

Can virtual water trade save water resources?

At times, certain areas of China suffering from water shortages. While China's government is spurring innovation and infrastructure to help head off such problems, it may be that some water conservation could help as well. It is well-known that water is embodied in traded goods-so called "virtual water trade" (VWT). In China, it seems that many water-poor areas are perversely engaged in VWT. Further, China is engaging in the global trend of fragmentation in production, even as an interregional phenomenon. Perhaps something could be learned about conserving or reducing VWT, if we knew where and how it is practiced. Given some proximate causes, perhaps viable policies could be formulated. To this end, we employ China's multiregional input-output tables straddling two periods to trace the trade of a given region's three types of goods: local final goods, local intermediate goods, and goods that shipped to other regions and countries. We find that goods traded interregionally in China in 2012 embodied 30.4% of all water used nationwide. Nationwide, water use increased substantially over 2007-2012 due to greater shipment volumes of water-intensive products. In fact, as suspected, the rise in value chain-related trade became a major contributing factor. Coastal areas tended to be net receivers of VWT from interior provinces, although reasons differed, e.g. Shanghai received more to fulfill final demand (67.8% of net inflow) and Zhejiang for value-chain related trade (40.2% of net inflow). In sum, the variety of our findings reveals an urgent need to consider trade types and water scarcity when developing water resource allocation and conservation policies.

The Reconciliation of Multiple Conflicting Estimates: Entropy-Based and Axiomatic Approaches.

When working with economic accounts it may occur that multiple estimates of a single datum exist, with different degrees of uncertainty or data quality. This paper addresses the problem of defining a method that can reconcile conflicting estimates, given best guess and uncertainty values. We proceeded from first principles, using two different routes. First, under an entropy-based approach, the data reconciliation problem is addressed as a particular case of a wider data balancing problem, and an alternative setting is found in which the multiple estimates are replaced by a single one. Afterwards, under an axiomatic approach, a set of properties is defined, which characterizes the ideal data reconciliation method. Under both approaches, the conclusion is that the formula for the reconciliation of best guesses is a weighted arithmetic average, with the inverse of uncertainties as weights, and that the formula for the reconciliation of uncertainties is a harmonic average.

Passenger rail security, planning, and resilience: application of network, plume, and economic simulation models as decision support tools.

We built three simulation models that can assist rail transit planners and operators to evaluate high and low probability rail-centered hazard events that could lead to serious consequences for rail-centered networks and their surrounding regions. Our key objective is to provide these models to users who, through planning with these models, can prevent events or more effectively react to them. The first of the three models is an industrial systems simulation tool that closely replicates rail passenger traffic flows between New York Penn Station and Trenton, New Jersey. Second, we built and used a line source plume model to trace chemical plumes released by a slow-moving freight train that could impact rail passengers, as well as people in surrounding areas. Third, we crafted an economic simulation model that estimates the regional economic consequences of a variety of rail-related hazard events through the year 2020. Each model can work independently of the others. However, used together they help provide a coherent story about what could happen and set the stage for planning that should make rail-centered transport systems more resistant and resilient to hazard events. We highlight the limitations and opportunities presented by using these models individually or in sequence.

Understanding the economic costs and benefits of catastrophes and their aftermath: a review and suggestions for the U.S. federal government.

The number and magnitude of devastating natural and human events make it imperative that we actively and systematically estimate the costs and benefits of policy decisions in affected localities, regions, states, and nations. Such strategic risk management preparedness efforts should forecast well into the future and include scenarios with and without enhanced engineered structures; with reduced vulnerability through land-use planning and design; with the impact of resiliency and mitigation; with evacuation and relocation; and with the costs and benefits of recovery and restoration. We describe different kinds of regional economic models that can be used in these preparedness planning efforts, explore critical data needs, and advocate a shared federal-state-local strategic planning effort to accomplish the objective.

Hydroxyl tagging velocimetry in a supersonic flow over a cavity.

Hydroxyl tagging velocimetry (HTV) measurements of velocity were made in a Mach 2 (M 2) flow with a wall cavity. In the HTV method, ArF excimer laser (193 nm) beams pass through a humid gas and dissociate H2O into H + OH to form a tagging grid of OH molecules. In this study, a 7 x 7 grid of hydroxyl (OH) molecules is tracked by planar laser-induced fluorescence. The grid motion over a fixed time delay yields about 50 velocity vectors of the two-dimensional flow in the plane of the laser sheets. Velocity precision is limited by the error in finding the crossing location of the OH lines written by the excimer tag laser. With a signal-to-noise ratio of about 10 for the OH lines, the determination of the crossing location is expected to be accurate within +/- 0.1 pixels. Velocity precision within the freestream, where the turbulence is low, is consistent with this error. Instantaneous, single-shot measurements of two-dimensional flow patterns were made in the nonreacting M 2 flow with a wall cavity under low- and high-pressure conditions. The single-shot profiles were analyzed to yield mean and rms velocity profiles in the M 2 nonreacting flow.