EFFECT OF REVENUE INSURANCE ON ENTRY AND EXIT DECISIONS IN TABLE GRAPE PRODUCTION: A REAL OPTION APPROACH

This study determines the entry and exit thresholds of table grape farming with irreversible investment under uncertainty. Real option approach is adopted to consider the investment and management flexibility. Also revenue insurance is introduced to consider the effect of the risk management programs on the entry and exit thresholds. Results show that revenue insurance increases the entry and exit thresholds by 1% and 4%, respectively, thus discouraging new investment and current farming, as long as the revenue guarantee is less than the exit threshold. Revenue insurance increases the entry threshold by 3% and decreases the exit threshold by 13% as long as the revenue guarantee is greater than the exit threshold. In this case, revenue insurance discourages the investment and encourages the current farmer to stay in farming, further. However, the decrease in the subsidy rate results in the increase in both entry and exit thresholds. Thus, the premium subsidy levels should be carefully considered if the policy objective is to encourage growers to shift to higher-value crops.Risk and Uncertainty,

Irrigation Technology Adoption in the Texas High Plains: A Real Options Approach

Water scarcity has been a significant issue for several decades in the Texas High Plains, with agriculture identified as the main activity contributing to this scarcity. To address this issue, much effort has been devoted to developing and encouraging adoption of sophisticated irrigation systems with high levels of water application efficiency, such as the low energy precision application (LEPA) system, subsurface drip irrigation (SDI), and variable rate irrigation (VRI). In this study, the economic feasibility of these irrigation systems is evaluated in cotton farming in the Texas High Plains using a real options approach. Results find that only the LEPA system is profitable under current conditions. The VRI system is profitable with high cotton prices (above $0.72/lb), while SDI is not profitable under any conditions explored.Resource /Energy Economics and Policy,

Effects of federal risk management programs on investment, production, and contract design under uncertainty

Agricultural producers face uncertain agricultural production and market conditions. Much of the uncertainty faced by agricultural producers cannot be controlled by the producer, but can be managed. Several risk management programs are available in the U.S. to help manage uncertainties in agricultural production, marketing, and finance. This study focuses on the farm level economic implications of the federal risk management programs. In particular, the effects of the federal risk management programs on investment, production, and contract design are investigated. The dissertation is comprised of three essays. The unifying theme of these essays is the economic analysis of crop insurance programs. The first essay examines the effects of revenue insurance on the entry and exit thresholds of table grape producers using a real option approach. The results show that revenue insurance decreases the entry and exit thresholds compared with no revenue insurance, thus increasing the investment and current farming operation. If the policy goal is to induce more farmers in grape farming, the insurance policy with a high coverage level and high subsidy rate is effective. In the second essay, a mathematical programming model is used to examine the effects of federal risk management programs on optimal nitrogen fertilizer use and land allocation simultaneously. Current insurance programs and the Marketing Loan Program increase the optimal fertilizer rate 2% and increase the optimal cotton acreage 119-130% in a Texas cotton-sorghum system. Assuming nitrogen is harmful to the environment and cotton requires higher nitrogen use, these risk management programs counteract federal environmental programs. The third essay uses a principal-agent model to examine the optimal contract design that induces the best effort from the farmer when crop insurance is purchased. With the introduction of crop insurance, the investorÂs optimal equity financing contract requires that the farmer bear more risk in order to have the incentive to work hard, which is achieved by increasing variable compensation and decreasing fixed compensation

A model‐based dead‐band compensation for the dual‐active‐bridge isolated bidirectional DC–DC converter

The dual active bridge (DAB)‐based isolated bidirectional converter has been used to realize bidirectional energy flow while offering needed isolation between the primary and secondary side: for example, the battery side and grid side of one plug‐in hybrid electric vehicle (PHEV). Even though the operation of a DAB‐based DC–DC converter is straightforward, various transient processes exist, such as the dead‐band effect, which deeply affects the dynamic performance of the converter in real world applications. Compensation of this effect is not easy because of the strong nonlinearity of the entire system. This paper quantitatively analyzed the dead‐band effect at different output powers, and presented a model‐based controller to realize the nonlinear dead‐band compensation strategy, which can effectively mitigate demerits of the traditional PI‐based control strategy. The proposed control algorithm is validated through theoretical simulation and experimental results. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86950/1/20690_ftp.pd

Catheter-associated bacteremia by Mycobacterium senegalense in Korea

BACKGROUND: Rapidly growing mycobacteria is recognized as one of the causative agents of catheter-related infections, especially in immunocompromised hosts. To date, however, Mycobacterium senegalense, which was known as the principal pathogen of bovine farcy, has not been reported in human infection. CASE PRESENTATION: We describe the first case of human infection by M. senegalense, which has caused catheter-related bloodstream infection in a cancer patient in Korea. The microorganism was identified by the 16S rRNA gene, rpoB, and 16S-23S rRNA gene internal transcribed spacer (ITS) sequence analyses. CONCLUSION: Our first report of catheter-associated bacteremia caused by M. senegalense suggests the zoonotic nature of this species and indicates the expansion of mycobacterial species relating to human infection. M. senegalense should be considered as one of the causes of human infections in the clinical practice

Cooperative translocation enhances the unwinding of duplex DNA by SARS coronavirus helicase nsP13

SARS coronavirus encodes non-structural protein 13 (nsP13), a nucleic acid helicase/NTPase belonging to superfamily 1 helicase, which efficiently unwinds both partial-duplex RNA and DNA. In this study, unwinding of DNA substrates that had different duplex lengths and 5′-overhangs was examined under single-turnover reaction conditions in the presence of excess enzyme. The amount of DNA unwound decreased significantly as the length of the duplex increased, indicating a poor in vitro processivity. However, the quantity of duplex DNA unwound increased as the length of the single-stranded 5′-tail increased for the 50-bp duplex. This enhanced processivity was also observed for duplex DNA that had a longer single-stranded gap in between. These results demonstrate that nsP13 requires the presence of a long 5′-overhang to unwind longer DNA duplexes. In addition, enhanced DNA unwinding was observed for gapped DNA substrates that had a 5′-overhang, indicating that the translocated nsP13 molecules pile up and the preceding helicase facilitate DNA unwinding. Together with the propensity of oligomer formation of nsP13 molecules, we propose that the cooperative translocation by the functionally interacting oligomers of the helicase molecules loaded onto the 5′-overhang account for the observed enhanced processivity of DNA unwinding

Direct Inhibition of GSK3β by the Phosphorylated Cytoplasmic Domain of LRP6 in Wnt/β-Catenin Signaling

Wnt/β-catenin signaling plays a central role in development and is also involved in a diverse array of diseases. Binding of Wnts to the coreceptors Frizzled and LRP6/5 leads to phosphorylation of PPPSPxS motifs in the LRP6/5 intracellular region and the inhibition of GSK3β bound to the scaffold protein Axin. However, it remains unknown how GSK3β is specifically inhibited upon Wnt stimulation. Here, we show that overexpression of the intracellular region of LRP6 containing a Ser/Thr rich cluster and a PPPSPxS motif impairs the activity of GSK3β in cells. Synthetic peptides containing the PPPSPxS motif strongly inhibit GSK3β in vitro only when they are phosphorylated. Microinjection of these peptides into Xenopus embryos confirms that the phosphorylated PPPSPxS motif potentiates Wnt-induced second body axis formation. In addition, we show that the Ser/Thr rich cluster of LRP6 plays an important role in LRP6 binding to GSK3β. These observations demonstrate that phosphorylated LRP6/5 both recruits and directly inhibits GSK3β using two distinct portions of its cytoplasmic sequence, and suggest a novel mechanism of activation in this signaling pathway

High-power bi-directional DC/DC converters with controlled device stresses

The objective of the research is to develop a cost-effective high-power bi-directional dc/dc converter with low total-device ratings, reduced system parasitic effects, and a wide input/output range. Additional objectives of the research are to develop a small-signal model and control methods, and to present performance characterizations. Device stresses in the proposed topology are controlled to maintain minimal levels by varying the duty ratio and phase-shift angle between the primary and the secondary bridges, which results in a low total-device rating, when compared to conventional bi-directional dc/dc topologies. In the proposed topology, soft switching, which reduces power loss, can be realized under specific operating conditions. When the condition that causes minimal device stress is satisfied, zero-voltage switching (ZVS) can be obtained. In the research, ZVS capability is explored for a wide range of voltage conditions as well as for the minimal device-stress condition. The performance characterization includes verifying the soft-switching regions and power-loss estimation. Another part of the thesis is the controller design of the converter. Small-signal models and feedback controllers are developed, and the controllers are experimentally validated. Because in the isolated high-frequency converters, transformer saturation is an important issue, a method to prevent transformer saturation is proposed and experimentally validated.Ph.D

Allocation of NTS (Non-Traffic Sensitive) Deficit in Telecommunications

The cost in telecommunications industry can be divided into NTS (Non-Traffic Sensitive) cost and TS (Traffic Sensitive) cost. In principle, consumers bear the NTS cost by paying subscription charge and the TS cost by paying per-call charge. It is well known that when one considers network externality. it is socially optimal to charge subscription charge lower than the NTS cost and per-call charge higher than the TS cost. The resulting NTS deficit has been conventionally compensated by the profits from the TS sector. If competition is introduced under this situation, it will necessarily be introduced into the TS sector (cf. cream skimming). In this case, the regulator confronts the question of whether new entrants should cross subsidize incumbent's NTS deficit. If so, on what basis could it be shared among new entrants? Currently in Korea, NTS deficit is allocated amongst new entrants in proportion to access traffic. However, this method has been under controversy. This paper explores the question of the optimal NTS deficit allocation. The conclusions are; first, it is appropriate for new entrants to bear the deficit; second, allocation according to demand elasticity and traffic is more efficient than the current method; and third, when the price is fixed by the regulator, allocation based on the traffic is justifiable

Models of Interconnection in Telecommunications

We proposed and utilized a simple model to review relay interconnection literatures. Without any complications of scale economies and opportunity costs, marginal cost pricing of interconnection charge is optimal. When incumbent sets the interconnection charge, it may or may not foreclose entrants depending upon degree of entrant's efficiency and forms of interconnection charge. When there are opportunity costs for incumbent to interconnect, then opportunity cost should be paid by the entrant according to the efficient component pricing rule. When there are economies of scale, Ramsey pricing comes to rescue. In an extension of Ramsey spirit, the global price caps are suggested. Next, we have reviewed the current status of the two-way access theory. First, a case of collusive retail prices has been presented even when the market competition exists between symmetric networks. In this case, the use of two-part tariffs or price discrimination can help, as they enable firms to compete in market shares without affecting their access payments. Various types of Internet interconnection are presented along with main results by Laffont, Marcus, Rey and Tirole (2001a, b) on the pricing issues of Internet interconnection