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Abstract

The relationship between internal response-based reliability and conditionality is investigated for Gauss-Markov (GM) models with uncorrelated observations. The models with design matrices of full rank and of incomplete rank are taken into consideration. The formulas based on the Singular Value Decomposition (SVD) of the design matrix are derived which clearly indicate that the investigated concepts are independent of each other. The methods are presented of constructing for a given design matrix the matrices equivalent with respect to internal response-based reliability as well as the matrices equivalent with respect to conditionality. To analyze conditionality of GM models, in general being inconsistent systems, a substitute for condition number commonly used in numerical linear algebra is developed, called a pseudo-condition^number. Also on the basis of the SVD a formula for external reliability is proposed, being the 2-norm of a vector of parameter distortions induced by minimal detectable error in a particular observation. For systems with equal nonzero singular values of the design matrix, the formula can be expressed in terms of the index of internal response-based reliability and the pseudo-condition^number. With these measures appearing in explicit form, the formula shows, although only for the above specific systems, the character of the impact of internal response-based reliability and conditionality of the model upon its external reliability. Proofs for complementary properties concerning the pseudo-condition^number and the 2-norm of parameter distortions in systems with minimal constraints are given in the Appendices. Numerical examples are provided to illustrate the theory.
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Authors and Affiliations

Witold Prószyński
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Abstract

Though normal air cooling and green sand mold-casted gray iron convey an essentially pearlitic matrix, ferritic gray iron is used in some electro-mechanical applications to have better magnetic properties, ductility, and low hardness. Conventionally, to produce ferritic gray iron, foundryman initially produces pearlitic gray iron, then it is carried through a long annealing cycle process for ferritic transformation. This experiment is conducted to eliminate the long annealing cycle from the conventional process. A process is developed to produce as-cast ferritic gray cast iron by air cooling in the green sand mold. In this experiment, Si content is kept high, but Mn content is kept low based on sulfur content; a unique thermodynamic process is established for decreasing the Mn content from the melt. After a successful preconditioning and optimum foundry return charging, the melt is specially inoculated, and metal is poured into the green sand mold. An extra feeder is added for slowing down the cooling rate where casting thickness is around 15mm. Finally, hardness and metallographic images are observed for final confirmation of the ferritic matrix.
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Bibliography

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[14] Stefanescu, D. M., Alonso, G., & Suarez, R. (2020). Recent developments in understanding nucleation and crystallization of spheroidal graphite in iron-carbon-silicon alloys. Metals. 10(2), 221. DOI: 10.3390/met10020221.
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Authors and Affiliations

Md Sojib Hossain
1

  1. Bangladesh University of Engineering and Technology, Shahbagh, Dhaka – 1000, Bangladesh
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Abstract

Irreversibility analysis was investigated by using refrigerants R22, R407A, and R407C in window type air conditioner system. The experimental study was conducted at various ambient temperatures and air volumetric flow rates to determine the parameters that cause the energy degradation of the system. The irreversibility was compared with respect to volumetric flow rates of the air passing through evaporator (14.15, 12.74, and 10.618 m3/min) and different ambient temperatures (ranging from 28 ◦C to 39 ◦C dry bulb. Results show that the total irreversibility increases with refrigerant mass flow rate and ambient temperature for the three refrigerants. Additionally, R22 shows the highest irreversibility in low ambient temperature (28 ◦C to 30 ◦C) while R407A shows the lowest one with ambient temperature ranging from 30 ◦C to 36 ◦C. Both tested refrigerants are very good replacement for R22 in terms of irreversibility and energy analysis and these results are more remarkable with R407A.

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Authors and Affiliations

Ayad Khudhair Al-Nadawi
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Abstract

Aiming at the problems of the negative sequence governance and regenerative braking energy utilization of electrified railways, a layered compensation optimization strategy considering the power flow of energy storage systems was proposed based on the railway power conditioner. The paper introduces the topology of the energy storage type railway power conditioner, and analyzes its negative sequence compensation and regenerative braking energy utilization mechanism. Considering the influence of equipment capacity and power flow of the energy storage system on railway power conditioner compensation effect, the objective function and constraint conditions of the layered compensation optimization of the energy storage type railway power conditioner were constructed, and the sequential quadratic programming method was used to solve the problem. The feasibility of the proposed strategy is verified by a multi-condition simulation test. The results show that the proposed optimization compensation strategy can realize negative sequence compensation and regenerative braking energy utilization, improve the power factor of traction substations when the system equipment capacity is limited, and it also has good real-time performance.
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Authors and Affiliations

Ying Wang
1
ORCID: ORCID
Yanqiang He
1
ORCID: ORCID
Xiaoqiang Chen
1
Miaomiao Zhao
1
Jing Xie
2

  1. School of Automation and Electrical Engineering, Lanzhou Jiaotong University, Lanzhou, 730070 China
  2. Xi’an Rail Transit Group Co., LTD Operation Branch Xi’an, 710000 China
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Abstract

In order to ensure that all the connected Equipment in the distribution network operates smoothly, the voltage stability of photovoltaic (PV) integrated distribution systems is very important. Sustaining the voltage profile when integrating PV is a particularly difficult issue. The primary goal of this article is to provide a consistent voltage profile to a sensitive load. A three-phase PV integrated distribution system has been chosen for investigation. An innovative feature of this system is that UPQC DVR and STATCOM systems are powered by Z-source inverters instead of traditional inverters. The ability to actively decouple power is the primary benefit of utilizing a Z-source inverter. The objective of the study effort is to use this new UPQC to synchronize a solar PV system with the distribution system. For the UPQC with battery energy storage system (BESS), the research study examines and develops the most appropriate control approach. A UPQC is a device that is used to integrate solar panels and improve the voltage stability of the distribution system. The prototype model is being developed, and the experimental findings confirm the main objective.
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Authors and Affiliations

A. Raja
1
M. Vijayakumar
2
C. Karthikeyan
3

  1. Electrical and Electronics Engineering Department, SSM College of Engineering, Kumarapalayam, Namakkal – 638 183, Tamilnadu, India
  2. Electrical and Electronics Engineering Department, K.S.R. College of Engineering, Tiruchengode, Namakkal-637 215, Tamilnadu, India
  3. Electrical Department, Tamil Nadu Generation and Distribution Corporation Ltd., Erode – 638009, Tamilnadu, India
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Abstract

In order to achieve energy savings and promote on-site integration of photovoltaic energy in electrified railways, a topology structure is proposed for the integration of photovoltaic (PV) and the energy storage system (ESS) into the traction power supply system (TPSS) based on a railway power conditioner (RPC). This paper analyzes the composition and operation principles of this structure. To assess the economic benefits brought by the integration of photovoltaic and energy storage systems, a bilevel optimization model is established, with the objectives of optimizing energy storage capacity configuration and photovoltaic energy integration. The KKT (Karush–Kuhn–Tucker) method is employed to transform the model into a single-layer mixed-integer linear programming model, which is then solved using the CPLEX solver in MATLAB. The research findings indicate that, with the configuration of the ESS, the optimal PV consumption rate achieved is 96.8749%. Compared to a 100% PV consumption rate, the ESS capacity configuration is reduced by 13.14%, and the overall operational cost of the TPSS is at its lowest. The study suggests that the proposed bilevel optimization algorithm can more effectively consider PV consumption, leading to enhanced economic performance of the TPSS operation.
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Authors and Affiliations

Wei Zhang
1
ORCID: ORCID
Xiaoqiang Chen
1
Ying Wang
1
ORCID: ORCID

  1. School of Automation and Electrical Engineering, Lanzhou Jiaotong University Lanzhou,730070 China

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