On Approaching the Ultimate Limits of Photon-Efficient and Bandwidth-Efficient Optical Communication

It is well known that ideal free-space optical communication at the quantum limit can have unbounded photon information efficiency (PIE), measured in bits per photon. High PIE comes at a price of low dimensional information efficiency (DIE), measured in bits per spatio-temporal-polarization mode. If only temporal modes are used, then DIE translates directly to bandwidth efficiency. In this paper, the DIE vs. PIE tradeoffs for known modulations and receiver structures are compared to the ultimate quantum limit, and analytic approximations are found in the limit of high PIE. This analysis shows that known structures fall short of the maximum attainable DIE by a factor that increases linearly with PIE for high PIE. The capacity of the Dolinar receiver is derived for binary coherent-state modulations and computed for the case of on-off keying (OOK). The DIE vs. PIE tradeoff for this case is improved only slightly compared to OOK with photon counting. An adaptive rule is derived for an additive local oscillator that maximizes the mutual information between a receiver and a transmitter that selects from a set of coherent states. For binary phase-shift keying (BPSK), this is shown to be equivalent to the operation of the Dolinar receiver. The Dolinar receiver is extended to make adaptive measurements on a coded sequence of coherent state symbols. Information from previous measurements is used to adjust the a priori probabilities of the next symbols. The adaptive Dolinar receiver does not improve the DIE vs. PIE tradeoff compared to independent transmission and Dolinar reception of each symbol.Comment: 10 pages, 8 figures; corrected a typo in equation 3

Mandatory waiting periods before abortion and sterilization: theory and practice

Some laws insist on a fixed, compulsory waiting period between the time of obtaining consent and when abortions or sterilizations are carried out. Waiting periods are designed to allow for reflection on the decision and to minimize regret. In fact, the cognitive processing needed for these important decisions takes place relatively rapidly. Clinicians are used to handling cases individually and tailoring care appropriately, including giving more time for decision-making. Psychological considerations in relation to the role of emotion in decision-making, eg, regret, raise the possibility that waiting periods could have a detrimental impact on the emotional wellbeing of those concerned which might interfere with decision-making. Having an extended period of time to consider how much regret one might feel as a consequence of the decision one is faced with may make a person revisit a stable decision. In abortion care, waiting periods often result in an extra appointment being needed, delays in securing a procedure and personal distress for the applicant. Some women end up being beyond the gestational limit for abortion. Those requesting sterilization in a situation of active conflict in their relationship will do well to postpone a decision on sterilization. Otherwise, applicants for sterilization should not be forced to wait. Forced waiting undermines people’s agency and autonomous decision-making ability. Low-income groups are particularly disadvantaged. It may be discriminatory when applied to marginalized groups. Concern about the validity of consent is best addressed by protective clinical guidelines rather than through rigid legislation. Waiting periods breach reproductive rights. Policymakers and politicians in countries that have waiting periods in sexual and reproductive health regulation should review relevant laws and policies and bring them into line with scientific and ethical evidence and international human rights law

The Configurable SAT Solver Challenge (CSSC)

It is well known that different solution strategies work well for different types of instances of hard combinatorial problems. As a consequence, most solvers for the propositional satisfiability problem (SAT) expose parameters that allow them to be customized to a particular family of instances. In the international SAT competition series, these parameters are ignored: solvers are run using a single default parameter setting (supplied by the authors) for all benchmark instances in a given track. While this competition format rewards solvers with robust default settings, it does not reflect the situation faced by a practitioner who only cares about performance on one particular application and can invest some time into tuning solver parameters for this application. The new Configurable SAT Solver Competition (CSSC) compares solvers in this latter setting, scoring each solver by the performance it achieved after a fully automated configuration step. This article describes the CSSC in more detail, and reports the results obtained in its two instantiations so far, CSSC 2013 and 2014

Smart thermostat

The current thermostat marketplace is dominated by programmable thermostats that are engineered to give the user as much control as possible. However, not all users program these thermostats optimally. Some prefer comfort over energy efficiency and will heat an empty house. Others do not care to program their thermostat and leave it at a set temperature. The Smart Thermostat that we have created is engineered to optimize the temperature for the user, using the common sense of the engineer to lower energy consumption. It uses a Raspberry Pi as a platform to implement a fuzzy logic control System. By removing the extensive control of the thermostat from the user we are able to create a more energy efficient product that also maintains the comfort level of the occupants

PPP in small towns' water supply in Uganda

PPP in small towns' water supply in Ugand

Bayesian Opponent Modeling in Multiplayer Imperfect-Information Games

In many real-world settings agents engage in strategic interactions with multiple opposing agents who can employ a wide variety of strategies. The standard approach for designing agents for such settings is to compute or approximate a relevant game-theoretic solution concept such as Nash equilibrium and then follow the prescribed strategy. However, such a strategy ignores any observations of opponents' play, which may indicate shortcomings that can be exploited. We present an approach for opponent modeling in multiplayer imperfect-information games where we collect observations of opponents' play through repeated interactions. We run experiments against a wide variety of real opponents and exact Nash equilibrium strategies in three-player Kuhn poker and show that our algorithm significantly outperforms all of the agents, including the exact Nash equilibrium strategies