Unsupervised Hashing via Similarity Distribution Calibration

Existing unsupervised hashing methods typically adopt a feature similarity preservation paradigm. As a result, they overlook the intrinsic similarity capacity discrepancy between the continuous feature and discrete hash code spaces. Specifically, since the feature similarity distribution is intrinsically biased (e.g., moderately positive similarity scores on negative pairs), the hash code similarities of positive and negative pairs often become inseparable (i.e., the similarity collapse problem). To solve this problem, in this paper a novel Similarity Distribution Calibration (SDC) method is introduced. Instead of matching individual pairwise similarity scores, SDC aligns the hash code similarity distribution towards a calibration distribution (e.g., beta distribution) with sufficient spread across the entire similarity capacity/range, to alleviate the similarity collapse problem. Extensive experiments show that our SDC outperforms the state-of-the-art alternatives on both coarse category-level and instance-level image retrieval tasks, often by a large margin. Code is available at https://github.com/kamwoh/sdc

Numerical Study of a High Temperature Latent Heat Storage (200-300 0 C) Using Eutectic Nitrate Salt of Sodium Nitrate and Potassium Nitrate

Abstract: In this study, a small scale direct solar thermal energy storage unit for a parabolic dish system with a secondary reflector is designed and developed. The main advantage of thermal energy storage is that thermal energy is available also during times when there is little or no sun shine. In addition, no heat transport fluid is needed in this system. A well insulated heat storage should keep the heat for about 24 hours. KNO 3 and NaNO 3 in 60:40 percent ratio (mol %) is used as latent heat storage material (PCM). This type of salt is also used in large scale solar power plants producing electricity. Effects of the heat flux and the number of fins on the latent heat storage charging process were numerically simulated using COMSOL Multiphysics. During phase change (melting) of the PCM, large amount of energy in the form of latent heat of fusion is needed. The phase change heat transfer was implemented using the effective heat capacity method

Heat and mass transfer studies of palm kernel cake (PKC) in fluidized bedfermenter

Solid state fermentation (SSF) which involves the growth of microorganism on moist solid substratesin the absence of free flowing water, has gained renewed attention over submerged fermentation forspecific applications. During the SSF process in fermenter, there are three main engineering problemsencountered such as the removal of metabolic heat from the substrate, diffusion of O2 and moisturethrough the substrate, and heterogeneity of the substrate and inoculum. A fluidized bed fermenter inwhich the particles move independently like a fluid was proposed to conduct the study. Throughoutthe study, rapid heat transfer from PKC to air was experimentally observed within the first 150s with atemperature drop of 30◦C. This indicated that the excellent heat transfer between palm kernel cake andairallowssolidstatefermentationofPKCwithoutaccumulationofmetabolicheatinthefermenter.Apartfrom heat removal, water adsorption study on PKC from air to bed was carried out.It showed that theincreaseofadsorbedwaterinPKCwasproportionaltoairrelativehumidityandinverselyproportionaltosuperficial air velocity. The maximum moisture content adsorbed by PKC under fluidization conditionswas around 10% (on dry basis). Finally, mathematical models for heat and mass transfer were proposedwhich can predict the experimental data quite satisfactoril