Commitment as investment under uncertainty

Irreversible investment and the techniques associated with pricing real options have led to significant advances many areas. We broaden this range of applications, showing how the techniques can apply to many policy problems in finance, macroeconomics, and trade policy. With small changes, standard techniques can handle a broad range of strategic problems related to policy. The decision to commit is like the decision to make an irreversible investment. Explicitly considering and correctly valuing the option to wait makes discretion relatively more attractive, implies that increased uncertainty increases the gain to discretion, and results in policy which displays hysteresis.Investments

Parallel Quantum-Point-Contacts as High-Frequency-Mixers

We present the results of high-frequency mixing experiments performed upon parallel quantum point-contacts defined in the two-dimensional electron gas of an Al_{x}Ga_{1-x}As/GaAs-heterostructure. The parallel geometry, fabricated using a novel double-resist technology, enables the point-contact device to be impedance matched over a wide frequency range and, in addition, increases the power levels of the mixing signal while simultaneously reducing the parasitic source-drain capacitance. Here, we consider two parallel quantum point-contact devices with 155 and 110 point-contacts respectively; both devices operated successfully at liquid helium and liquid nitrogen temperatures with a minimal conversion loss of 13 dB.Comment: 4 figures, RevTeX, to be published in the 16 June 1997 issue of Applied Physic Letter

Исследование накопления водорода в сплаве никелида титана при электролитическом наводороживании

В процессе работы проводилось насыщение образцов из сплава никелида титана электролитическим способом при разных температурах и плотностях тока с целью исследование факторов, которые влияют на его поглощение водорода. В результате исследований было определено, как эти факторы влияют на наводороживание.The effects of solution temperature, current density, grain size and charging time on the hydrogen absorption of Ni–Ti superelastic alloy immersed in 0.9% NaCl solution have been investigated systematically by hydrogen analyzer RHEN602. For hydrogen cathodic charging under constant current density, upon increasing solution temperature and charging time, the hydrogen concentration increased. As current density increases, the hydrogen concentration initially increases rapidly, then slightly changes. The grain size of materials also has an influence on the hydrogen absorption

Coherent coupling of two quantum dots embedded in an Aharonov-Bohm ring

We define two laterally gated small quantum dots (~ 15 electrons) in an Aharonov-Bohm geometry in which the coupling between the two dots can be broadly changed. For weakly coupled quantum dots we find Aharonov-Bohm oscillations. In an intermediate coupling regime we concentrate on the molecular states of the double dot and extract the magnetic field dependence of the coherent coupling.Comment: 6 pages, 4 figure

Economic modeling of the combined effects of HIV-disease, cholesterol and lipoatrophy based on ACTG 5142 trial data

<p>Abstract</p> <p>Background</p> <p>This study examines the cost and consequences of initiating an ARV regimen including Lopinavir/ritonavir (LPV/r) or Efavirenz (EFV), using data from a recent clinical trial in a previously published model of HIV-disease.</p> <p>Methods</p> <p>We populated the Markov model of HIV-disease with data from ACTG 5142 study to estimate the economic outcomes of starting ARV therapy with a PI-containing regimen as compared to an NNRTI-containing regimen, given their virologic and immunologic efficacy and effects on cholesterol and lipoatrophy. CNS toxicities and GI tolerability were not included in the model because of their transient nature or low cost remedies, and therefore lack of economic impact. CD4+ T-cell counts and the HIV-1 RNA (viral load) values from the study were used to assign a specific health state (HS) to each patient for each quarter year. The resulting frequencies used as "raw" data directly into the model obviate the reliance on statistical tests, and allow the model to reflect actual patient behavior in the clinical trial. An HS just below the last observed HS was used to replace a missing value.</p> <p>Results</p> <p>The modeled estimates (undiscounted) for the LPV/r-based regimen resulted in 1.41 quality-adjusted life months (QALMs) gained over a lifetime compared to the EFV-based regimen. The LPV/r-based regimen incurred $7,458 (1.8$88,829/QALY. Most of the higher costs accrue before the 7th year of treatment and were offset by subsequent savings. The estimates are highly sensitive to the effect of lipoatrophy on Health-related Quality of Life (HRQOL), but not to the effect of cholesterol levels.</p> <p>Conclusions</p> <p>The cost effectiveness of ARV regimens may be strongly affected by enduring AEs, such as lipoatrophy. It is important to consider specific AE effects from all drugs in a regimen when ARVs are compared.</p> <p>Trial registration</p> <p>(ClinicalTrials.gov number, <a href="http://www.clinicaltrials.gov/ct2/show/NCT00050895">NCT00050895</a><url>http://[ClinicalTrials.gov]</url>).</p

Investigation of DFIG with Fault RideThrough Capability

Abstract--In this paper, the ability of doubly fed induction generators to provide voltage stability support in weak transmission networks is investigated. Specifically, the response of wind turbines to voltage dips at the point of common coupling and its effects on system stability are analyzed. A control strategy for the operation of the grid and rotor side converters is developed in order to support the grid voltage by injecting reactive power during and after grid fault events. The performance of the strategy is analyzed for different voltage dips at the point of common coupling of a wind farm and compared with the case when the converters do not provide any voltage support. Simulations are performed using a simplified model of the Chilean transmission network. This system is considered to be a good example of weak power system, because of its radial configuration