Exploration and Practice of Nitrogen Addition Process for LF Refining Ladle Bottom Blowing Nitrogen Steel Liquid

This article discusses and analyzes the law of nitrogen increase in liquid steel and the main factors affect-ing the nitrogen increasing of molten steel,through the way of adding nitrogen to molten steel by bottom blowing nitrogen gas in LF refining process.It is considered that the main factors affecting the nitrogen increasing instability of molten steel are the initial temperature of LF refining,nitrogen relative element,surface active elements[O]and[S]of steel liquid,and bottom blowing rate of ladle.The large-scale production practice shows that T[O]not more than 50×10-6 and[S]is not more than 0.020 in LF refining at the initial temperature of not less than 1570.The liquid steel nitrogen enrichment test is carried out by ladle bottom blowing nitrogen gas after 20 min of refining,the flow rate is set as(6.0~7.0)NL/min per ton,and it is turned to 2 NL/min at 6 min before the end of refining,the nitrogen increasing rate of liquid steel is basically stable at(5~6)×10-6 per minute.

Environmental Impact Assessment System and Process in Developing Countries

Environmental impact assessment (EIA), a decision-making process for project appraisal and sustainability adopted globally as an administrative process to identify, predict, evaluate, and monitor projects from their feasibility, preconstruction, construction, and operation stages to mitigate the adverse impacts and enhance the beneficial impacts for the protection of the affected environment, The study objective is to explore global EIA systems and processes and find shortcomings and implications for making the best instrument or tool to protect the natural environment from man-made activities over the project cycle. For this, the relevant literature on the EIA system and process was reviewed and evaluated through the application of quantitative and qualitative approaches, including the assessment of legal instruments and the adoption of EIA methodologies in developing countries. EIA, initiated in the 1970s in the US and Australia, expanded to developing countries and was amended in East and Southeast Asia from the 1970s to the 2000s. The evaluation assessed that the South Asian countries follow UNEP and IAIA guidelines, utilizing national laws and expert consultations, with screening criteria and administrative processes based on established environmental legislation. Ad hoc, checklist, matrix, network, overlay, cost-benefit analysis, and predictive or simulation in EIA practice are used to assess the environmental impacts of development activities. Failure to recommend major projects undermines public trust and prevents mitigation measures from being implemented. Most developing countries have followed EIA to fulfill the legal requirement with shadow-off monitoring and follow-up rather than to upset, reduce, or compensate for the project impacts as per size, location, and severity of the project area. The research and guidelines outlined in the IAIA principles and process have synthesized the best EIA practices worldwide. Public participation, impact coverage, scientific mitigation, transparent evidence-based approaches, monitoring, follow-up, legitimate approaches, and future appraisal opportunities are major concerns to be included in best EIA practice.

Research on Staged Practice Teaching System Based on Systems Engineering

The practical teaching management system is an important factor to ensure the quality of teaching.The training of systematic thinking needs a systematic teaching system,and a systematic process is a gradual process and a standardized process.This paper discusses the process of establishing a standardized practice teaching system step by step through a progressive way.At the same time,taking test practice as an example,it describes how the practice teaching system enables students to gradually adapt to and benefit from the management of the system.Through project practice,students not only enhance their practical ability,but also learn the standardized practice process.These skills can help students adapt to the work pace of the enterprise faster,and make students’practical ability meet the requirements of the enterprise.

Evolution Handoff Strategy for Real-Time Video Transmission over Practical Cognitive Radio Networks

The transmission delay of realtime video packet mainly depends on the sensing time delay(short-term factor) and the entire frame transmission delay(long-term factor).Therefore,the optimization problem in the spectrum handoff process should be formulated as the combination of microscopic optimization and macroscopic optimization.In this paper,we focus on the issue of combining these two optimization models,and propose a novel Evolution Spectrum Handoff(ESH)strategy to minimize the expected transmission delay of real-time video packet.In the microoptimized model,considering the tradeoff between Primary User's(PU's) allowable collision percentage of each channel and transmission delay of video packet,we propose a mixed integer non-linear programming scheme.The scheme is able to achieve the minimum sensing time which is termed as an optimal stopping time.In the macro-optimized model,using the optimal stopping time as reward function within the partially observable Markov decision process framework,the EHS strategy is designed to search an optimal target channel set and minimize the expected delay of packet in the long-term real-time video transmission.Meanwhile,the minimum expected transmission delay is obtained under practical cognitive radio networks' conditions,i.e.,secondary user's mobility,PU's random access,imperfect sensing information,etc..Theoretical analysis and simulation results show that the ESH strategy can effectively reduce the transmission delay of video packet in spectrum handoff process.

Letters A practical method of interpolation for real time processing

A simple way of interpolation for real time processing is pres -ented. For passive localization, the time delay between two signals can be determined by the peak of their cross-correlation. It is more efficient to estimate a cross-correlation function by the inverse FFT of the cross-spectral density. The original smapling rate is usually very low to reduce computation. The sampling rate of the cross-correlation so computed is too low to estimate satisfactorily and an interpolation procedure is therefore needed. The interpolation by zero augmented spectrum is concise, fast and accurate. The results of the computer simulation and real nuderwater signal processing are given in the paper.