812 research outputs found
Investigation of a Data Split Strategy Involving the Time Axis in Adverse Event Prediction Using Machine Learning
Adverse events are a serious issue in drug development and many prediction
methods using machine learning have been developed. The random split
cross-validation is the de facto standard for model building and evaluation in
machine learning, but care should be taken in adverse event prediction because
this approach tends to be overoptimistic compared with the real-world
situation. The time split, which uses the time axis, is considered suitable for
real-world prediction. However, the differences in model performance obtained
using the time and random splits are not fully understood. To understand the
differences, we compared the model performance between the time and random
splits using eight types of compound information as input, eight adverse events
as targets, and six machine learning algorithms. The random split showed higher
area under the curve values than did the time split for six of eight targets.
The chemical spaces of the training and test datasets of the time split were
similar, suggesting that the concept of applicability domain is insufficient to
explain the differences derived from the splitting. The area under the curve
differences were smaller for the protein interaction than for the other
datasets. Subsequent detailed analyses suggested the danger of confounding in
the use of knowledge-based information in the time split. These findings
indicate the importance of understanding the differences between the time and
random splits in adverse event prediction and suggest that appropriate use of
the splitting strategies and interpretation of results are necessary for the
real-world prediction of adverse events.Comment: 20 pages, 4 figure
Regional Inequality Simulations Based on Asset Exchange Models with Exchange Range and Local Support Bias
To gain insights into the problem of regional inequality, we proposed new
regional asset exchange models based on existing kinetic income-exchange models
in economic physics. We did this by setting the spatial exchange range and
adding bias to asset fraction probability in equivalent exchanges. Simulations
of asset distribution and Gini coefficients showed that suppressing regional
inequality requires, firstly an increase in the intra-regional economic
circulation rate, and secondly the narrowing down of the exchange range
(inter-regional economic zone). However, avoiding over-concentration of assets
due to repeat exchanges requires adding a third measure; the local support bias
(distribution norm). A comprehensive solution incorporating these three
measures enabled shifting the asset distribution from over-concentration to
exponential distribution and eventually approaching the normal distribution,
reducing the Gini coefficient further. Going forward, we will expand these
models by setting production capacity based on assets, path dependency on
two-dimensional space, bias according to disparity, and verify measures to
reduce regional inequality in actual communities.Comment: 14 pages, 8 figures. Published online at
http://redfame.com/journal/index.php/aef/article/view/494
Control of particle circulation rate in circulating fluidized bed by a pulsed gas flow
As a coal-fired power generation technology for further improvement of power generation efficiency of coal-fired power generation, exergy regeneration type coal gasification power generation technology (1), a triple-bed circulating fluidized bed (2), has been proposed.
The authors analyzed the flow characteristics of the triple-bed circulating fluidized bed, it has the flow characteristics of the riser and downer perform the proposed approach to representation by the equivalent circuit model. The equivalent circuit model of the riser and downer are shown in Figure 1. This equivalent circuit has the nature of the low-pass filter. A combination of the low-pass filter and the pulse voltage is used as a switching power supply. Then, we applied that the pulsed gas supply to the riser combined with a low-pass filter characteristics to control the particle circulation rate of the triple-bed circulating fluidized bed.
Figure 2 shows the input output characteristics of the equivalent circuit of the riser/downer inputting a pulse voltage. We used an electric circuit simulator SPICE to calculation of circuit behavior. Circuit constant is to use the value of the reference 3, the input pulse height is set to 80V. When the input pulse width is changed, the output current is changed depending on the pulse width. Moreover, when changing the density of the pulse, the output current is changing depending on the pulse density. This result by giving a pulsed gas supply to the riser, it shows the possibility controlling the particle circulation rate of the triple-bed circulating fluidized bed.
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Investigation of agglomerates growth mechanism for thermal seawater desalination
Desalination technology has been paid large attention because water demand has been increasing due to the industrial development and high growth rate of population. To develop a novel desalination process with high energy efficiency and with high recovery ratio, a self-heat recuperative seawater desalination process using a fluidized-bed evaporator has been proposed (1). The fluidized-bed evaporator was employed to prevent scale deposition on the heat transfer surface during seawater evaporation. The seawater evaporation experiment using a lab-scale fluidized bed showed that the proposed evaporator prevents scale deposition on the heat transfer surface (2). However, it was also found that the seawater feed into the bed causes agglomeration of fluidized particles, which has the possibility to cause defluidization.
In this research, seawater evaporation experiments using the lab-scale fluidized-bed evaporator were conducted and the influence of operating conditions such as fluidizing gas velocity, seawater feed rate and bed temperature on the agglomeration behavior of fluidized particles was examined. Furthermore, the mechanism of agglomerates growth was investigated and the optimal operating conditions of the fluidized bed for thermal desalination were examined.
REFERENCES H. Mizuno, Y. Kansha, M. Ishizuka and A. Tsutsumi. A Novel Thermal Desalination Process Using Fluidized Bed. Chem. Eng. Trans., 39: 181-186, 2014 H. Mizuno, Y. Kansha, M. Ishizuka and A. Tsutsumi. Agglomeration behavior in fluidized-bed evaporator for thermal seawater desalination. Appl. Therm. Eng., 89: 1096-1103, 2015
Difficulty in learning chirality for Transformer fed with SMILES
Recent years have seen development of descriptor generation based on
representation learning of extremely diverse molecules, especially those that
apply natural language processing (NLP) models to SMILES, a literal
representation of molecular structure. However, little research has been done
on how these models understand chemical structure. To address this, we
investigated the relationship between the learning progress of SMILES and
chemical structure using a representative NLP model, the Transformer. The
results suggest that while the Transformer learns partial structures of
molecules quickly, it requires extended training to understand overall
structures. Consistently, the accuracy of molecular property predictions using
descriptors generated from models at different learning steps was similar from
the beginning to the end of training. Furthermore, we found that the
Transformer requires particularly long training to learn chirality and
sometimes stagnates with low translation accuracy due to misunderstanding of
enantiomers. These findings are expected to deepen understanding of NLP models
in chemistry.Comment: 20 pages, 6 figure
Development of Rotary Compressor for High-efficiency CO2 Heat-pump Hot-Water Supply System
In Japan, there has been an increase in the use of domestic heat-pump hot-water supply systems in which the refrigerant is CO2, which does not cause ozone layer depletion and has a low global-warming potential. In addition, in recent years, there has been an increase in the number of examples in which CO2 is employed as a refrigerant for showcase refrigerators, freezers etc. Therefore, in the future, it is expected that there will be an increasing demand for CO2 compressors with greater efficiency and lower noise. In the case of domestic heat-pump hot-water supply systems, in order to increase the annual performance factor (APF) of a product, it is effective to enhance the coefficient of performance (COP) in an intermediate capacity range. Here, we report the development of a high-APF rotary compressor achieved by optimizing the design specifications of a motor and a discharge pathway from a discharge chamber, for operation in the intermediate capacity range. In the optimization process, in order to cope with the high operating pressure of the CO2 water-heating cycle, we performed analysis using the finite element method (FEM) for evaluating the stiffness around the discharge port. In addition, we used an FEM model of the entire compressor in a modal analysis, and, in analyzing the radiation surfaces of the rotary compressor, we used an acoustic particle velocity probe that is capable of measuring the intensity at an intermediate portion between the accumulator and the compressor main unit, where it has been difficult to take measurements in the past. We also discuss an example in which noise reduction was confirmed when the specifications of the accumulator were changed based on the results of these analyses
Generating Shuttling Procedures for Constrained Silicon Quantum Dot Array
In silicon quantum computers, a single electron is trapped in a
microstructure called a quantum dot, and its spin is used as a qubit. For
large-scale integration of qubits, we previously proposed an approach of
arranging the quantum dots in a two-dimensional array and sharing a control
gate in a row or column of the array. In our array, the shuttling of electrons
is a useful technique to operate the target qubit independently and avoid
crosstalk. However, since the shuttling is also conducted using shared control
gates, the movement of qubits is complexly constrained. We therefore propose a
formal model on the basis of state transition systems to describe those
constraints and operation procedures on the array. We also present an approach
to generate operation procedures under the constraints. Utilizing this
approach, we present a concrete method for our 16 8 quantum dot array.
By implementing the proposed method as a quantum compiler, we confirmed that it
is possible to generate operation procedures in a practical amount of time for
arbitrary quantum circuits. We also demonstrated that crosstalk can be avoided
by shuttling and that the fidelity in that case is higher than when crosstalk
is not avoided
Non-Equilibrium Fluidization of Dense Active Suspension
We investigate dense suspensions of swimming bacteria prepared in a
nutrient-exchange chamber. Near the pellet concentration, nonthermal
fluctuations showed notable agreement between self and collective behaviors, a
phenomenon not previously observed at equilibrium. The viscosity of active
suspensions dramatically decreased compared to their inactive counterparts,
where glassy features, such as non-Newtonian viscosity and dynamic
heterogeneity, disappeared. Instead, the complex shear modulus showed a
power-law rheology,,
indicating the role of bacterial activity in driving the system towards a
critical jamming state
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