A Numerical Study of Heat Transfer from an Array of Jets Impinging on a Flat Moving Surface

Numerical study of heat transfer between circular jet arrays and the flat moving surface is carried out. Two jet patterns: inline and staggered, are chosen. Total nine circular jets are used in both jet patterns. The analysis is carried out for steady-state and transient conditions with the turbulent flow of jet fluid. In steady-state analysis, the influence of surface motion on the flow field and heat transfer by the array of jets is analyzed. The surface-to-jet velocity ratio (r) varies from 0 to 2. In transient analysis, the effect of jet pattern on the cooling of hot moving plate is analyzed. The two-equation shear stress transport (SST) k-? turbulence model is used for solving Reynolds averaged Navier-Stokes (RANS) equations of conservation of mass, momentum, and energy for incompressible turbulent flow. The steady-state analysis shows that surface motion has a significant effect on the flow field and heat transfer. The transient analysis results show that a staggered jet pattern cools the plate more uniformly than an inline jet pattern.

Interpretation of NO₃–N₂O₅ observation via steady state in high aerosol air mass: The impact of equilibrium coefficient in ambient conditions

Steady state approximation for interpreting NO3 and N2O5 has large uncertainty under complicated ambient conditions and could even produces incorrect results unconsciously. To provide an assessment and solution to the dilemma, we formulate data sets based on in-situ observations to reassess the applicability of the method. In most of steady state cases, we find a prominent discrepancy between Keq (equilibrium coefficient for reversible reactions of NO3 and N2O5) and correspondingly simulated [N2O5]/([NO2]×[NO3]), especially in wintertime high aerosol conditions. This gap reveals the accuracy of Keq has a critical impact on the steady state analysis in polluted region. In addition, the accuracy of γ(N2O5) derived by steady state fit depends closely on the reactivity of NO3 (kNO3) and N2O5 (kN2O5). Based on a complete set of simulations, air mass of kNO3 less than 0.01 s−1 with high aerosol and temperature higher than 10 °C is suggested to be the best suited for steady state analysis of NO3–N2O5 chemistry. Instead of confirming the validity of steady state by numerical modeling for every case, this work directly provides concentration ranges appropriate for accurate steady state approximation, with implications for choosing suited methods to interpret nighttime chemistry in high aerosol air mass.

Steady State Analysis of Impulse Customers and Cancellation Policy in Queueing-Inventory System

This article discusses the queueing-inventory model with a cancellation policy and two classes of customers. The two classes of customers are named ordinary and impulse customers. A customer who does not plan to buy the product when entering the system is called an impulse customer. Suppose the customer enters into the system to buy the product with a plan is called ordinary customer. The system consists of a pool of finite waiting areas of size N and maximum S items in the inventory. The ordinary customer can move to the pooled place if they find that the inventory is empty under the Bernoulli schedule. In such a situation, impulse customers are not allowed to enter into the pooled place. Additionally, the pooled customers buy the product whenever they find positive inventory. If the inventory level falls to s, the replenishment of Q items is to be replaced immediately under the (s, Q) ordering principle. Both arrival streams occur according to the independent Markovian arrival process (MAP), and lead time follows an exponential distribution. In addition, the system allows the cancellation of the purchased item only when there exist fewer than S items in the inventory. Here, the time between two successive cancellations of the purchased item is assumed to be exponentially distributed. The Gaver algorithm is used to obtain the stationary probability vector of the system in the steady-state. Further, the necessary numerical interpretations are investigated to enhance the proposed model.

SBMLWebApp: Web-Based Simulation, Steady-State Analysis, and Parameter Estimation of Systems Biology Models

In systems biology, biological phenomena are often modeled by Ordinary Differential Equations (ODEs) and distributed in the de facto standard file format SBML. The primary analyses performed with such models are dynamic simulation, steady-state analysis, and parameter estimation. These methodologies are mathematically formalized, and libraries for such analyses have been published. Several tools exist to create, simulate, or visualize models encoded in SBML. However, setting up and establishing analysis environments is a crucial hurdle for non-modelers. Therefore, easy access to perform fundamental analyses of ODE models is a significant challenge. We developed SBMLWebApp, a web-based service to execute SBML-based simulation, steady-state analysis, and parameter estimation directly in the browser without the need for any setup or prior knowledge to address this issue. SBMLWebApp visualizes the result and numerical table of each analysis and provides a download of the results. SBMLWebApp allows users to select and analyze SBML models directly from the BioModels Database. Taken together, SBMLWebApp provides barrier-free access to an SBML analysis environment for simulation, steady-state analysis, and parameter estimation for SBML models. SBMLWebApp is implemented in Java™ based on an Apache Tomcat® web server using COPASI, the Systems Biology Simulation Core Library (SBSCL), and LibSBMLSim as simulation engines. SBMLWebApp is licensed under MIT with source code freely available. At the end of this article, the Data Availability Statement gives the internet links to the two websites to find the source code and run the program online.

Transformer-Less Switched-Capacitor Quasi-Switched Boost DC-DC Converter

In this article, a quasi-switched boost converter based on the switched-capacitor technique with high step-up voltage capability is dealt with and analyzed. The proposed converter offers a simple structure and low voltage stress on the semiconductor elements with intrinsic small duty cycle. An inductor of the proposed converter is connected in series with the input voltage source; therefore, continuous input current ripple is attainable. In addition, the efficiency of the proposed converter is also improved. A detailed steady-state analysis is discussed to identify the salient features of the switched-capacitor-based quasi-switched boost DC-DC converter. The performance of the converter is compared against similar existing high boost DC-DC converters. Finally, the switched-capacitor-based quasi-switched boost DC-DC converter is investigated by experimental verification.

A Unique Electrical Model for the Steady-State Analysis of a Multi-Energy System

In order to decarbonize the energy sector, the interdependencies between the power and natural gas systems are going to be much stronger in the next period. Thus, it is necessary to have a powerful simulation model that is able to efficiently and simultaneously solve all coupled energy carriers in a single simulation environment in only one simulation step. As an answer to the described computational challenges, a unique model for the steady-state analysis of a multi-energy system (MES) using the electrical analogy approach is developed. Detailed electrical equivalent models, developed using the network port theory and the load flow method formulation, of the most important natural gas network elements, as well as of the linking facilities between the power and natural gas systems, are given. The presented models were loaded up into a well-known software for the power system simulation—NEPLAN. In the case studies, the accuracy of the presented models is confirmed by the comparison of the simulation results with the results obtained by SIMONE—a well-known software for natural gas network simulations. Moreover, the applicability of the presented unique model is demonstrated by the MES security of a supply analysis.