Distill-and-Compare: Auditing Black-Box Models Using Transparent Model Distillation

Black-box risk scoring models permeate our lives, yet are typically proprietary or opaque. We propose Distill-and-Compare, a model distillation and comparison approach to audit such models. To gain insight into black-box models, we treat them as teachers, training transparent student models to mimic the risk scores assigned by black-box models. We compare the student model trained with distillation to a second un-distilled transparent model trained on ground-truth outcomes, and use differences between the two models to gain insight into the black-box model. Our approach can be applied in a realistic setting, without probing the black-box model API. We demonstrate the approach on four public data sets: COMPAS, Stop-and-Frisk, Chicago Police, and Lending Club. We also propose a statistical test to determine if a data set is missing key features used to train the black-box model. Our test finds that the ProPublica data is likely missing key feature(s) used in COMPAS.Comment: Camera-ready version for AAAI/ACM AIES 2018. Data and pseudocode at https://github.com/shftan/auditblackbox. Previously titled "Detecting Bias in Black-Box Models Using Transparent Model Distillation". A short version was presented at NIPS 2017 Symposium on Interpretable Machine Learnin

Potential for water distillation by using solar energy in Malawi

The potential for solar water distillation in Malawi has been modelled. Mean monthly global solar radiation (H) data from 19 sites spread all over the country was used to compute the mean monthly daily distillate productivity (M). Results show that H varies from 15.3 MJ m*-2 to 27.8 MJ m*-2 while M varies from 1.0 kg m*-2 to 2.5 kg m*-2. Distillate productivity is high (up to 2.5 kg m*-2) during the dry season, in phase with the shortage of water supply. It appears that there is enormous potential for harnessing solar radiation to improve the quality of drinking water in the country

Computation of irradiance in a solar still by using a refined algorithm

A refined solar algorithm from the ESP-r system has been used to calculate the distribution of solar irradiation inside a basin-type solar still. In the approach, surface finish, view factors and multiple reflections are taken into consideration in the computation of the solar radiation that reaches the surface of the saline water in the distillation system. The algorithm was applied to a solar still tested at the University of Strathclyde in Glasgow (55 520 N, 4 150 W). Under the prevailing meteorological conditions, it was found that previous models overestimated the computed solar load on the saline water surface. The present modelling approach is demonstrated to exhibit a higher degree of accuracy than previous methods for irradiance distribution prediction, yielding new insights into approaches to solar still performance improvement. The modelling outcomes are presented and discussed

Model for computation of solar fraction in a single-slope solar still

A new model that calculates the distribution of solar radiation inside a single-slope solar still has been proposed. In this model, the solar fraction on a vertical surface is divided into beam and diffuse parts and the optical view factors of surfaces inside the still are taken into account. To validate the model, outdoor tests of a conventional solar still were conducted under different weather conditions at the University of Strathclyde. The proposed model is compared with the previous one. It is found that the beam solar fraction is affected by both the geometry of the solar still and position of the sun in the sky. In contrast, the diffuse solar fraction is only dependent on the geometry of the solar distiller. The present model exhibited a lower root mean square error than that of the previous model. It appears that splitting the solar fraction into beam and diffuse parts improves the accuracy of modelling the performance of a single-slope solar still

Turbulent heat transfer in spacer-filled channels: Experimental and computational study and selection of turbulence models

Heat transfer in spacer-filled channels of the kind used in Membrane Distillation was studied in the Reynolds number range 100–2000, encompassing both steady laminar and early-turbulent flow conditions. Experimental data, including distributions of the local heat transfer coefficient h, were obtained by Liquid Crystal Thermography and Digital Image Processing. Alternative turbulence models, both of first order (k-ε, RNG k-ε, k-ω, BSL k-ω, SST k-ω) and of second order (LRR RS, SSG RS, ω RS, BSL RS), were tested for their ability to predict measured distributions and mean values of h. The best agreement with the experimental results was provided by first-order ω-based models able to resolve the viscous/conductive sublayer, while all other models, and particularly ε-based models using wall functions, yielded disappointing predictions

Numerical study of a passive solar still with separate condenser

A passive solar still with separate condenser has been modeled and its performance evaluated. The system has one basin in the evaporation chamber and two basins (middle and upper) in the condenser chamber, with a glass cover over the evaporator basin and an opaque condensing cover over the upper basin. The evaporator, middle and upper basins yield the first, second and third effects respectively. The top part of the condensing cover is shielded from solar radiation to keep the cover relatively cool. Water vapor from the first effect condenses under the glass cover while the remainder of it flows into the condenser, by purging and diffusion, and condenses under the liner of the middle basin. The performance of the system is evaluated and compared with that of a conventional solar still under the same meteorological conditions. Results show that the distillate productivity of the present still is 62% higher than that of the conventional type. Purging is the most significant mode of vapor transfer from the evaporator into the condenser chamber. The first, second and third effects contribute 60, 22 and 18% of the total distillate yield respectively. It is also found that the productivity of the solar still with separate condenser is sensitive to the absorptance of the evaporator basin liner, mass of water in the evaporator and middle basins, and wind speed. The mass of water in the upper basin has a marginal effect on distillate production. Other results are presented and discussed in detail

Optimisation of operating parameters for the removal of ethanol from Zingiber officinale Roscoe (ginger) oleoresin using short-path distillation

Due to the importance of exploiting the natural sources to enhance healthier lifestyle, cultivated herbs such as Zingiber Officinale Roscoe or ginger has become our main interest in this research in order to accomplish all the objectives mentioned. Using a statistical software called MINITAB, optimisation on short-path distillation experiments was done and the results showed that feed temperature, along with evaporating temperature and distillate rate were the three operational parameters that influenced the purification process of ginger oleoresin. Feed temperature should be set at 65°C and the evaporating temperature also at the same temperature to maximise the oleoresin concentration. The result of the study also point to the advantages and efficiency of feed pre-heating to temperature close or equals to that of evaporating temperature under steady-state conditions for the given operating conditions, prior to its entering the evaporation surface. Although feed rate effect is not statistically significant, it does have linear effect on the oleoresin concentration. The vast difference between theoretical separation efficiency and calculated separation efficiency was probably due to the thickness of liquid film, initial concentration and viscosity of the liquid feed. The theoretical value of recovery yield at feed and evaporating temperature of 65°C is 0.99, and experimental value of recovery yield is 0.95. Based on this integrated knowledge on various type of ginger samples, pre-processing methods and more importantly the experience of applying technologies in optimising final purification of ginger oleoresin, would serve to enhance the transfer of advanced technology to local producers

Reaction Dynamics with Exotic Beams

We review the new possibilities offered by the reaction dynamics of asymmetric heavy ion collisions, using stable and unstable beams. We show that it represents a rather unique tool to probe regions of highly Asymmetric Nuclear Matter ($ANM$) in compressed as well as dilute phases, and to test the in-medium isovector interaction for high momentum nucleons. The focus is on a detailed study of the symmetry term of the nuclear Equation of State ($EOS$) in regions far away from saturation conditions but always under laboratory controlled conditions. Thermodynamic properties of $ANM$ are surveyed starting from nonrelativistic and relativistic effective interactions. In the relativistic case the role of the isovector scalar $\delta$-meson is stressed. The qualitative new features of the liquid-gas phase transition, "diffusive" instability and isospin distillation, are discussed. The results of ab-initio simulations of n-rich, n-poor, heavy ion collisions, using stochastic isospin dependent transport equations, are analysed as a function of beam energy and centrality. The isospin dynamics plays an important role in all steps of the reaction, from prompt nucleon emissions to the final fragments. The isospin diffusion is also of large interest, due to the interplay of asymmetry and density gradients. In relativistic collisions, the possibility of a direct study of the covariant structure of the effective nucleon interaction is shown. Results are discussed for particle production, collective flows and iso-transparency. Perspectives of further developments of the field, in theory as well as in experiment, are presented.Comment: 167+5 pages, 77 figures, general revie

Metal-loaded organic scintillators for neutrino physics

Organic liquid scintillators are used in many neutrino physics experiments of the past and present. In particular for low energy neutrinos when realtime and energy information are required, liquid scintillators have several advantages compared to other technologies. In many cases the organic liquid needs to be loaded with metal to enhance the neutrino signal over background events. Several metal loaded scintillators of the past suffered from chemical and optical instabilities, limiting the performance of these neutrino detectors. Different ways of metal loading are described in the article with a focus on recent techniques providing metal loaded scintillators that can be used under stable conditions for many years even in ton scale experiments. Applications of metal loaded scintillators in neutrino experiments are reviewed and the performance as well as the prospects of different scintillator types are compared.Comment: 46 pages, 5 figure

Have policy distortion spilled overacross wine markets ? : evidence from the french wine sector

This paper investigates cross-market effects of policy instruments that were implemented in the table and quality wine market as one of the pillars of market intervention in Europe’s Common Market Organisation (CMO) for wine. We explore two hypotheses regarding the spill-over of distillation policy distortions and quality downgrading. Empirical evidence from France, the largest producer of quality wines in Europe, provides support for the hypothesis that distillation policy distortions in the quality wine market have spilledover to the table wine market. As predicted by our second hypothesis, we find evidence for quality downgrading, a phenomenon that has so far received little attention in the wine economics literature.Common market organization for wine, distillation, spill-over effects, quality downgrading, France, heterogeneous panel