The balanced tensor product of module categories

The balanced tensor product M (x)_A N of two modules over an algebra A is the vector space corepresenting A-balanced bilinear maps out of the product M x N. The balanced tensor product M [x]_C N of two module categories over a monoidal linear category C is the linear category corepresenting C-balanced right-exact bilinear functors out of the product category M x N. We show that the balanced tensor product can be realized as a category of bimodule objects in C, provided the monoidal linear category is finite and rigid.Comment: 19 pages; v3 is author-final versio

Collusion with secret price cuts: an experimental investigation

Theoretical work starting with Stigler (1964) suggests that collusion may be difficult to sustain in a repeated game with secret price cuts and demand uncertainty. Compared to equilibria in games of perfect information, trigger-strategy equilibria in this context result in lower payoffs because punishments occur along the equilibrium path. We tested the theory in a series of economic experiments. Consistent with the theory, treatments with imperfect information were less collusive than treatments with perfect information. However, in the imperfect-information treatments, players seemed to settle on the static Nash outcome rather than using trigger strategies. Players did resort to punishments for undercutting in perfect-information treatments, and this sometimes led to successful collusion afterward.

Why Are Drugs More Profitable Than Vaccines?

In a simple representative consumer model, vaccines and drug treatments yield the same revenue for a pharmaceutical manufacturer, implying that the firm would have the same incentive to develop either ceteris paribus. We provide more realistic models in which the revenue equivalence breaks down for two reasons. First, drug treatments are sold after the firm has learned who has contracted the disease; in the case of heterogeneous consumers who vary with respect to the probability of contracting the disease, there is less asymmetric information to prevent the firm from extracting consumer surplus with drug treatments than with vaccines. We prove that, due to this aspect of pharmaceutical pricing, the ratio of drug-treatment to vaccine revenue can be arbitrarily high; we calculate that the ratio is about two to one for empirical distributions of HIV risk. The second reason for the breakdown of revenue equivalence is that vaccines are more likely to interfere with the spread of the disease than are drug treatments, thus reducing demand for the product. By embedding an economic model within a standard dynamic epidemiological model, we show that the steady-state flow of revenue is greater for drug treatments than for vaccines.

Effects of chemical equilibrium on turbine engine performance for various fuels and combustor temperatures

A study was performed to quantify the differences in turbine engine performance with and without the chemical dissociation effects for various fuel types over a range of combustor temperatures. Both turbojet and turbofan engines were studied with hydrocarbon fuels and cryogenic, nonhydrocarbon fuels. Results of the study indicate that accuracy of engine performance decreases when nonhydrocarbon fuels are used, especially at high temperatures where chemical dissociation becomes more significant. For instance, the deviation in net thrust for liquid hydrogen fuel can become as high as 20 percent at 4160 R. This study reveals that computer central processing unit (CPU) time increases significantly when dissociation effects are included in the cycle analysis

The Navy/NASA Engine Program (NNEP89): A user's manual

An engine simulation computer code called NNEP89 was written to perform 1-D steady state thermodynamic analysis of turbine engine cycles. By using a very flexible method of input, a set of standard components are connected at execution time to simulate almost any turbine engine configuration that the user could imagine. The code was used to simulate a wide range of engine cycles from turboshafts and turboprops to air turborockets and supersonic cruise variable cycle engines. Off design performance is calculated through the use of component performance maps. A chemical equilibrium model is incorporated to adequately predict chemical dissociation as well as model virtually any fuel. NNEP89 is written in standard FORTRAN77 with clear structured programming and extensive internal documentation. The standard FORTRAN77 programming allows it to be installed onto most mainframe computers and workstations without modification. The NNEP89 code was derived from the Navy/NASA Engine program (NNEP). NNEP89 provides many improvements and enhancements to the original NNEP code and incorporates features which make it easier to use for the novice user. This is a comprehensive user's guide for the NNEP89 code

The design and performance estimates for the propulsion module for the booster of a TSTO vehicle

A NASA study of the propulsion systems for possible low-risk replacements for the Space Shuttle is presented. Results of preliminary studies to define the USAF two-stage-to-orbit (TSTO) concept to deliver 10,000 pounds to low polar orbit are described. The booster engine module consists of an over/under turbine bypass engines/ramjet engine design for acceleration from takeoff to the staging point of Mach 6.5 and approximately 100,000 feet altitude. Propulsion system performance and weight are presented with preliminary mission study results of vehicle size