A General Simulation Framework for Supply Chain Modeling: State of the Art and Case Study

Nowadays there is a large availability of discrete event simulation software that can be easily used in different domains: from industry to supply chain, from healthcare to business management, from training to complex systems design. Simulation engines of commercial discrete event simulation software use specific rules and logics for simulation time and events management. Difficulties and limitations come up when commercial discrete event simulation software are used for modeling complex real world-systems (i.e. supply chains, industrial plants). The objective of this paper is twofold: first a state of the art on commercial discrete event simulation software and an overview on discrete event simulation models development by using general purpose programming languages are presented; then a Supply Chain Order Performance Simulator (SCOPS, developed in C++) for investigating the inventory management problem along the supply chain under different supply chain scenarios is proposed to readers.Comment: International Journal of Computer Science Issues online at http://ijcsi.org/articles/A-General-Simulation-Framework-for-Supply-Chain-Modeling-State-of-the-Art-and-Case-Study.ph

Energy and Economic Performance Analysis of Heat Recovery Devices Under Different Climate Conditions

High performance buildings typically relies on extreme envelope performances in terms of insulation level, solar gains valorization and airtightness. The energy needs are limited and the system sizing is reduced to increase the recourse to renewable energy sources. The only exception to this trend is related to the ventilation, which is even more crucial because of the infiltration control. Mechanical ventilation is a common option to ensure an appropriate ventilation rate and a suitable indoor air quality. Heat recovery devices are widely used to save energy in buildings mechanical ventilation systems. Their contribution in the design or operating phases is typically assessed in terms of effectiveness, which expresses the ratio between the amount of energy – sensible and/or total – actually recovered and the maximum recoverable under ideal configuration. However the effectiveness of recovery devices is not a constant value and depends on the operating – outdoor and indoor –conditions and control strategy. In order to evaluate the energy and cost savings allowed by heat recovery systems, these aspects have to be considered, and their relative impact on different heat recovery technologies accounted for. In this work, some of them are analyzed in detail and their contribution to the device effectiveness is discussed. The objective is to understand the influence of the air conditions (fresh and exhaust) on the energy savings considering different sensible and total heat recovery devices and operative constraints which could affect the control strategy. The analysis starts from hourly weather data, representative of different climate types, to quantify the actual effectiveness of different heat recovery systems. The impact of indoor conditions on the sensible and latent recovery is analyzed, defining appropriate control strategies to prevent excessive moisture recovery and discomfort issues when the indoor humidity is considered. Moreover, the effect of condensation and frosting on the hourly and annual performance of each kind of devices is analyzed. Three different climatic conditions have been considered. Sensible fixed-plate cross flow heat recovery system have been compared with enthalpy wheels By means of a parameterization of the operating constraints and the expression of the main quantities in specific terms, depending only on the building use, it has been possible to generalize the main results, making them independent of a specific case study, and to compare different technologies and climatic contexts. Seasonal and annual energy and economic performances have been quantified, as well as their sensitivity to specific calculation assumptions, such as the building type, the investment and energy costs, providing a synthetic overview of the technical and economic viability of the considered technologies and a geographic mapping of their competitiveness

Comparison Between The Performance Of Sensible And Total Heat Recovery Devices And A Liquid Desiccant Twin-Tower System

A significant share of the energy demand in high performance buildings is related to mechanical ventilation. Aside traditional heat recovery devices, liquid desiccant system can play a role. The performance of liquid desiccant devices and consequently their potential in energy savings is complex to estimate due to the influence of process parameters as well as the physical parameters of the fluids. A simple twin-tower configuration has been proposed as a reference system for assessing the control strategy and the potential of this technology to reduce the ventilation load. It consists of one absorption tower that treats the outside air and one that uses the exhaust air to regenerate the liquid desiccant. This configuration acts as a heat exchanger between the outlet and exhaust air streams with the liquid desiccant as heat and mass transfer medium. The heat and mass transfer between the fluid flows in the two towers has been modelled, and the energy saving potential in heating and cooling mode has been calculated based on annual hourly weather data. In order to assess the results, a comparison with the savings potential by sensible and total heat recovery have been performed considering 66 locations across Europe. Limitation and control strategies have been considered to prevent excessive indoor humidity considering different indoor latent load and airchange rates

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Erythrocyte's aging in microgravity highlights how environmental stimuli shape metabolism and morphology

The determination of the function of cells in zero-gravity conditions is a subject of interest in many different research fields. Due to their metabolic unicity, the characterization of the behaviour of erythrocytes maintained in prolonged microgravity conditions is of particular importance. Here, we used a 3D-clinostat to assess the microgravity-induced modifications of the structure and function of these cells, by investigating how they translate these peculiar mechanical stimuli into modifications, with potential clinical interest, of the biochemical pathways and the aging processes. We compared the erythrocyte's structural parameters and selected metabolic indicators that are characteristic of the aging in microgravity and standard static incubation conditions. The results suggest that, at first, human erythrocytes react to external stimuli by adapting their metabolic patterns and the rate of consumption of the cell resources. On longer timeframes, the cells translate even small differences in the environment mechanical solicitations into structural and morphologic features, leading to distinctive morphological patterns of agin

Saturated R134a flow boiling inside a 4.3 mm inner diameter microfin tube

The refrigerant charge minimization in refrigerating and air-conditioning systems represents a challenging issue due to the new environmental national and international regulations. The use of smaller smooth tubes, such as with the outer diameter around 5 mm, is becoming more and more common in many applications. More recently, the microfin tubes have also started to be reduced in size to cope with the continuously increasing demand of new, efficient, and compact heat exchangers for air-conditioning and refrigeration equipment. This work investigates the performance of R134a during saturated flow boiling inside a microfin tube with internal diameter at the fin tip of 4.3 mm. Boiling heat transfer coefficients, frictional pressure drops, and critical vapor qualities were measured at 30\ub0C of saturation temperature, by varying the refrigerant mass velocity between 100 and 800 kg m 122 s 121 and the vapor quality from 0.1 to 0.95 at four different heat fluxes: 15, 30, 60, and 90 kW m 122. Moreover, the reliability of several models for flow boiling heat transfer and pressure drop estimations was assessed by comparing the experimental results with the calculations

A Numerical Analysis Of Latent Thermal Energy Storage For Refrigerated Trucks

In this work, an innovative insulated wall concept for refrigerated truck is proposed. A 2D transient numerical model of the truck cell is developed and simulated considering the solar radiation from 6 AM to 4 PM of a typical summer day in Vicenza (Italy). The innovative composite wall consists of a traditional polyurethane (PU) insulation layer wrapping a layer of PCM (reference melting temperature of 2 °C) with different thickness from 0.5 cm to 2 cm. The results confirm that the proposed solution is very promising because even the smallest thickness can assure an adequate temperature inside the cell for almost the entire simulated journey

Toward the Development of a Hybrid Active and Measuring Exoskeleton for Upper Limbs of Heavy-duty Harbor Workers

The paper presents the study of a novel exoskeleton designed for the upper limbs of heavy-duty port operators responsible for lashing containers. This exoskeleton is designed to measure initially its configuration and operational times, once positioned on the workers, to pass to a partial activeness introducing motors for the shoulder, the intra-extra rotation of the forearm, and the elbow. The key concept revolves around the shoulder joint, with particular emphasis on the scapula and its motion. The scapula plays a fundamental role in moving the center of rotation of the humerus, contributing to its exceptional mobility. The fundamental objective is to develop a system that provides support for the vertical motion of the operator's arms, with a specific focus on allowing initially the vertical motion of the scapula to remain unrestricted. This approach aims to collect essential data, which, in a subsequent phase, will likely enable the addition of vertical support to the scapula, possibly with the assistance of AI. Meanwhile, the horizontal motion will consistently be left unrestricted. This exoskeleton design is inspired by previous work that conceptualized a fully measuring exoskeleton, and a corresponding patent application has been presented