A Review on Technologies for the Use of CO2 as a Working Fluid in Refrigeration and Power Cycles

The use of carbon dioxide as a working fluid has been the subject of extensive studies in recent years, particularly in the field of refrigeration where it is at the heart of research to replace CFC and HCFC. Its thermodynamic properties make it a fluid of choice in the efficient use of energy at low and medium temperatures in engine cycles. However, the performance of transcritical CO2 cycles weakens under high temperature and pressure conditions, especially in refrigeration systems;On the other hand, this disadvantage becomes rather interesting in engine cycles where CO2 can be used as an alternative to the organic working fluid in small and medium-sized electrical systems for low quality or waste heat sources. In order to improve the performance of systems operating with CO2 in the field of refrigeration and electricity production, research has made it possible to develop several concepts, of which this article deals with a review of the state of the art, followed by analyzes in-depth and critical of the various developments to the most recent modifications in these fields. Detailed discussions on the performance and technical characteristics of the different evolutions are also highlighted as well as the factors affecting the overall performance of the systems studied. Finally, perspectives on the future development of the use of CO2 in these different cycles are presented.

Regenerative Braking Energy Recovery System of Metro Train Based on Dual-Mode Power Management

In order to fully utilize the regenerative braking energy of metro trains and stabilize the metro DC traction busbar voltage,a hybrid regenerative braking energy recovery system with a dual-mode power management strategy is proposed.Firstly,the construction of the hybrid regenerative braking energy recovery system is explained.Then,based on the power demand of low-voltage load in metro stations,a dual-mode power management strategy is proposed to allocate the reference power of each system according to the different working conditions,and the control methods of each system are set.Finally,the correctness and effectiveness of the dual-mode strategy are verified through simulation,and the proposed braking energy utilization scheme is compared with other singleform utilization schemes.The results illustrate that the hybrid system with the dual-mode strategy can effectively recycle the regenerative braking energy of metro train and inhibit the busbar voltage fluctuation;the proposed braking energy utilization scheme has certain advantages on energy recovery and DC bus voltage stabilization compared with other single-form schemes;the proposed power management strategy can correctly allocate the reference power of each system with a lower construction cost.

Assessment of Axial Power Peaking Factors in GHARR-1 LEU Core: A Decadal Simulation Analysis

This study aims to thoroughly investigate the axial power peaking factors (PPF) within the low-enriched uranium (LEU) core of the Ghana Research Reactor-1 (GHARR-1). This study uses advanced simulation tools, like the MCNPX code for analysing neutron behavior and the PARET/ANL code for understanding power variations, to get a clearer picture of the reactor’s performance. The analysis covers the initial six years of GHARR-1’s operation and includes projections for its whole 60-year lifespan. We closely observed the patterns of both the highest and average PPFs at 21 axial nodes, with measurements taken every ten years. The findings of this study reveal important patterns in power distribution within the core, which are essential for improving the safety regulations and fuel management techniques of the reactor. We provide a meticulous approach, extensive data, and an analysis of the findings, highlighting the significance of continuous monitoring and analysis for proactive management of nuclear reactors. The findings of this study not only enhance our comprehension of nuclear reactor safety but also carry significant ramifications for sustainable energy progress in Ghana and the wider global context. Nuclear engineering is essential in tackling global concerns, such as the demand for clean and dependable energy sources. Research on optimising nuclear reactors, particularly in terms of safety and efficiency, is crucial for the ongoing advancement and acceptance of nuclear energy.

Probabilistic Global Maximum Power Point Tracking Algorithm for Continuously Varying Partial Shading Conditions on Autonomous PV Systems

A photovoltaic (PV) string with multiple modules with bypass diodes frequently deployed on a variety of autonomous PV systems may present multiple power peaks under uneven shading. For optimal solar harvesting, there is a need for a control schema to force the PV string to operate at global maximum power point (GMPP). While a lot of tracking methods have been proposed in the literature, they are usually complex and do not fully take advantage of the available characteristics of the PV array. This work highlights how the voltage at operating point and the forward voltage of the bypass diode are considered to design a global maximum power point tracking (GMPPT) algorithm with a very limited global search phase called Fast GMPPT. This algorithm successfully tracks GMPP between 94% and 98% of the time under a theoretical evaluation. It is then compared against Perturb and Observe, Deterministic Particle Swarm Optimization, and Grey Wolf Optimization under a sequence of irradiance steps as well as a power-over-voltage characteristics profile that mimics the electrical characteristics of a PV string under varying partial shading conditions. Overall, the simulation with the sequence of irradiance steps shows that while Fast GMPPT does not have the best convergence time, it has an excellent convergence rate as well as causes the least amount of power loss during the global search phase. Experimental test under varying partial shading conditions shows that while the GMPPT proposal is simple and lightweight, it is very performant under a wide range of dynamically varying partial shading conditions and boasts the best energy efficiency (94.74%) out of the 4 tested algorithms.

基于King达标理论的培训方案对临床护士叙事能力及人文关怀能力的影响

目的:探讨基于King达标理论构建临床护士叙事护理培训方案对临床护士叙事护理能力、人文关怀能力及共情能力的影响。方法:2023年3月—5月选取淄博市某三级甲等医院138名护士,采用随机数字表法分为试验组和对照组。对照组实施常规叙事护理培训,试验组在对照组的基础上实施基于King达标理论指导下的叙事护理方案。采用医学叙事能力量表(NCS)、关怀能力评价量表(CAI)、杰弗逊共情量表(JSE-HP)进行效果评价。结果:干预后,试验组护士NCS、CAI及JSE-HP得分均高于对照组,差异均有统计学意义(P<0.05)。结论:基于King达标理论构建的临床护士叙事培训方案可有效提高临床护士叙事护理能力、促进人文关怀能力并提升护士共情能力。

ICU患者置入Power PICC导管特殊异位原因分析

目的:探讨ICU患者置入Power PICC导管后头端反折向上至同侧和对侧锁骨下静脉、头臂静脉等特殊异位的相关因素。方法:回顾性分析2021年9月至2022年9月某三甲医院ICU 520例PICC置管患者,通过胸部X线确定PICC导管头端反折向上至对侧和同侧锁骨下静脉、头臂静脉的患者,分析其特殊异位发生因素。结果:胸部X线结果显示25例患者PICC管头端反折向上异位至对侧和同侧锁骨下静脉、头臂静脉或颈内静脉,异位发生率4.8%,不同静脉置管反折异位发生率相比差异无统计学意义,P>0.05。结论:ICU患者PICC置入发生导管头端反折向上至同侧和对侧锁骨下静脉、头臂静脉等特殊异位的发生因素较多,包括同时留置CVC或血透管、正在滴注或泵入多种药物、PICC管头端异位的隐匿性、导管材质、自身疾病及机械通气等危险因素。

A fuzzy control and neural network based rotor speed controller for maximum power point tracking in permanent magnet synchronous wind power generation system

When the wind speed changes significantly in a permanent magnet synchronous wind power generation system,the maximum power point cannot be easily determined in a timely manner.This study proposes a maximum power reference signal search method based on fuzzy control,which is an improvement to the climbing search method.A neural network-based parameter regulator is proposed to address external wind speed fluctuations,where the parameters of a proportional-integral controller is adjusted to accurately monitor the maximum power point under different wind speed conditions.Finally,the effectiveness of this method is verified via Simulink simulation.

Power-V诱导的钻柱黏滑振动特征分析

黏滑是石油钻井过程中影响钻井效率和井下钻柱安全的一种振动形式.垂直钻井系统Power-V在提供有效控斜力的同时,还会诱导钻柱黏滑振动.通过研究垂直钻井系统Power-V与井壁的接触作用及钻头与地层的相互作用模型,基于钻柱动力学有限元方法,深入分析Power-V的作用机理,研究其对扭转振动的影响,指出Power-V和井壁间的相互作用会导致钻柱与井壁的摩阻显著增加,进而引起摩阻扭矩的增大,诱导井下黏滑振动.实测振动数据证实,Power-V与井壁间的相互作用是引起钻柱黏滑振动的关键因素.这对于揭示黏滑振动的成因和更好地发挥Power-V的作用具有重要意义.

基于调和概率语言术语集的Power平均算子

实践发现现存概率语言Power平均算子在应用中存在概率信息丢失、计算过于繁琐等问题,针对这些问题,提出一种基于调和概率语言术语集的Power平均算子。结合新的基本运算法则与新的支撑度,给出新的概率语言Power平均算子、概率语言Power几何平均算子、概率语言Power加权平均算子、概率语言Power加权几何平均算子,同时论证分析了这几类新型算子的性质。最后通过实验数据,将提出的算子与现存算子进行对比分析,验证了所提算子的有效性与可行性。

基于King达标理论的心肺康复训练对高血压合并冠心病患者心肺适能及血压的影响

目的 探讨基于King达标理论的心肺康复训练对高血压合并冠心病患者心肺适能及血压的影响。方法 采用随机数字表法将84例高血压合并冠心病患者分为对照组(n=42)和试验组(n=42)。对照组采用常规康复治疗,试验组在常规康复治疗基础上加入心肺康复训练,两组均持续12周。干预后,比较两组干预前后心功能(LVEF、FS、BNP、VO2max、AT、METS)、肺功能(FVC、FEV1/FVC)、血压及运动自我效能的变化。结果 与干预前比较,干预12周后,两组LVEF、FS、VO2max、AT、METS、FVC、FEV1/FVC水平及运动自我效能感得分较干预前升高,且试验组升高幅度均大于对照组(均P<0.001);两组血浆BNP、收缩压、舒张压水平均降低,且试验组降低幅度大于对照组(均P<0.05)。结论 基于King达标理论的心肺康复训练能够显著提高高血压合并冠心病患者的心肺功能,降低患者血压,增强机体运动功能,促进心血管疾病康复。

数据可视化Power BI在职业院校学生管理中的应用

职业院校学生管理是一个重要而复杂的任务,需要学校管理人员的精心组织和有效执行。随着信息技术的发展和校园信息化建设的需求,部分职业院校的学生管理服务系统已初步建成。BI数据可视化可以有效地利用大量的系统数据,为院校管理者提高决策和治理水平提供依据。本文通过对BI数据可视化过程和结构进行分析,比较Power BI与传统型BI的差异,通过对Power BI数据可视化在职业院校学生管理中的应用分析和实践案例,验证数据可视化PowerBI在学生管理中的重要作用。

基于GT-Power的排气轰鸣噪声控制与优化研究

针对某1.5T三缸发动机车型排气尾管噪声在1 280 r/min、1 550 r/min转速下出现轰鸣声的问题,对其排气系统消声器结构进行优化设计,从而达到消除该轰鸣声的目标。分析了排气尾管轰鸣声的产生原因,并解释了轰鸣产生的机理,得出该轰鸣声是消声器在96~116 Hz下消声量不足的结论。通过GT-Power软件基于传递损失仿真结果优化了排气系统消声器结构,并建立发动机模型,与优化后的排气系统模型进行噪声仿真,仿真结果满足优化要求。在整车半消声室中进行了排气尾管噪声测试试验,测试结果验证了分析结果的准确性,且优化方案排气尾管轰鸣声消失,中高转速下噪声降低2 dB(A)

Power BI在我院药品数据可视化中的应用

目的加强医院药品精细化管理,提升药师对药品的数据分析能力,实现数据分析自动化及查询功能,为集采药品、麻精药品的动态监管提供数据支撑。方法使用数据可视化工具Power BI搭建服务,制作报表,能够查询药品使用情况和对比情况,实现各科室药品使用情况的可视化管理。结果通过该软件,药师可以精确查询任意时间维度下药品的使用数量、金额等情况,实现数据分析自动化。结论借助数据管理工具能够帮助药师提升数据分析能力和工作效率,有助于加强医院药品的精细化管控。

基于King互动达标理论在产科护士分层培训与教育中的应用及效果研究

目的 研究基于King互动达标理论在产科护士分层培训与教育中的应用及效果。方法 选取2021年1—12月本院正式在岗并在产科病区工作满1年及以上的N0-N4级护理人员64名为本次研究对象。依据随机化分组方法分成试验组和对照组,每组32名。试验组中的32名护理人员以King互动达标理论为基础的培训内容、并在317护APP平台接受培训。对照组中的32名护理人员接受教师讲解与示范操作式的传统护士分层与教育方式。对比两组的培训成绩、自主学习能力、注册护士核心能力。结果 教学后,试验组的培训成绩要高于对照组(P<0.05);试验组的自主学习能力明显优于对照组(P<0.05);试验组的注册护士核心能力明显强于对照组(P<0.05)。结论 基于King互动达标理论在产科护士分层培训与教育中的有效应用,可以在很大程度上强化护士的学习主观能动性,使不同层次的护士可以在培训与教育中收获更多理论知识与实践技能,提高培训成绩,强化学习能力与注册护士核心能力,增加晋升机会,减轻压力,增强职业归属感。

Carbon emission reduction:Contribution of photovoltaic power and practice in China

As a clean and renewable form of energy,photovoltaic(PV)power generation converts solar energy into electrical energy,reducing the consumption of fossil fuels and significantly lowering greenhouse gas emissions.Amidst the global transition towards cleaner forms of energy,countries all around the world are vigorously developing PV technology.

Traction power systems for electrified railways:evolution,state of the art,and future trends

Traction power systems(TPSs)play a vital role in the operation of electrified railways.The transformation of conventional railway TPSs to novel structures is not only a trend to promote the development of electrified railways toward high-efficiency and resilience but also an inevitable requirement to achieve carbon neutrality target.On the basis of sorting out the power supply structures of conventional AC and DC modes,this paper first reviews the characteristics of the existing TPSs,such as weak power supply flexibility and low-energy efficiency.Furthermore,the power supply structures of various TPSs for future electrified railways are described in detail,which satisfy longer distance,low-carbon,high-efficiency,high-reliability and high-quality power supply requirements.Meanwhile,the application prospects of different traction modes are discussed from both technical and economic aspects.Eventually,this paper introduces the research progress of mixed-system electrified railways and traction power supply technologies without catenary system,speculates on the future development trends and challenges of TPSs and predicts that TPSs will be based on the continuous power supply mode,employing power electronic equipment and intelligent information technology to construct a railway comprehensive energy system with renewable energy.

基于Power BI的DRGs数据分析方法

目的:探讨利用Power BI工具对DRGs数据进行有效分析,揭示潜在的数据特征和规律。方法:运用Power BI工具对2017年―2021年DRGs数据进行数据连接、数据清洗和处理等操作,提取和计算相关DRGs评价指标,最后通过可视化展示的方式对DRGs数据进行分析和呈现,从不同维度和角度深入研究DRGs数据特征和规律。结果:通过对2017年―2021年DRGs数据处理和可视化展示,能直观了解出院患者疾病构成、医疗资源利用、临床质量评估和医疗成本效益等总体情况,为提高医疗服务质量和资源利用效率等提供可行的解决方案。结论:基于Power BI的DRGs数据分析方法能够有效地帮助医院进行医疗费用控制和资源配置,并提高医疗服务的质量和效率。此方法为优化DRGs数据管理和医疗资源配置提供了重要的参考和借鉴价值。

King达标理论在慢性病家庭护理中应用的范围综述

目的 系统整合King达标理论在慢性病家庭护理中应用的相关研究,了解其目前的应用特征,分析其在家庭护理中的作用及不足,以期为今后相关研究的实施和推广提供参考。方法 采用范围综述的研究方法,系统检索PubMed、Embase、The Cochrane Library、Web of Science、中国知网、万方、维普以及中国生物医学文献数据库中有关King达标理论在慢性病家庭护理中应用的研究,检索时限均为建库至2024年2月2日,对最终纳入的文献进行数据提取、收集、总结并报告研究结果。结果 共纳入20项研究,从研究目的、研究对象、研究设计及结局指标等进行整理分析。结论 基于King达标理论的慢性病家庭护理方案具有积极的应用效果,但当前仍存在一些不足。未来研究应明确理论内涵,立足我国本土文化特征,朝研究方法多样化、应用形式多元化的方向发展,构建科学严谨的慢性病家庭护理干预方案及评价体系,进而形成符合我国国情的慢性病家庭护理模式。

Power BI在移民信息管理中的应用研究

信息技术的应用是提高水利工程移民信息化水平的重要手段,针对现有移民信息管理系统灵活性和通用性低的问题,分析了微软Power BI系列软件实现移民信息管理的可行性。以山东省老岚水库移民项目为例,使用该软件依次快捷完成移民信息的收集、整理和分析工作,并设计出交互式可视化界面,从多个维度展示和查询各类移民信息以及实现移民数据的多端实时共享。研究表明:运用Power BI系列软件虽然在结合地理信息方面仍存在不足,但能够以较低的使用难度和投入成本完成移民信息管理及可视化工作,提高工作效率。验证了其在移民信息管理方面的实用性和适用性,具备一定的推广价值。

Field test of high-power microwave-assisted mechanical excavation for deep hard iron ore

Microwave-assisted mechanical excavation has great application prospects in mines and tunnels,but there are few field experiments on microwave-assisted rock breaking.This paper takes the Sishanling iron mine as the research object and adopts the self-developed high-power microwave-induced fracturing test system for hard rock to conduct field experiments of microwave-induced fracturing of iron ore.The heating and reflection evolution characteristics of ore under different microwave parameters(antenna type,power,and working distance)were studied,and the optimal microwave parameters were obtained.Subsequently,the ore was irradiated with the optimal microwave parameters,and the cracking effect of the ore under the action of the high-power open microwave was analyzed.The results show that the reflection coefficient(standing wave ratio)can be rapidly(<5 s)and automatically adjusted below the preset threshold value(1.6)as microwave irradiation is performed.When using a right-angle horn antenna with a working distance of 5 cm,the effect of automatic reflection adjustment reaches the best among other antenna types and working distances.When the working distance is the same,the average temperature of the irradiation surface and the area of the high-temperature area under the action of the two antennas(right-angled and equal-angled horn antenna)are basically the same and decrease with the increase of working distance.The optimal microwave parameters are:a right-angle horn antenna with a working distance of 5 cm.Subsequently,in further experiments,the optimal parameters were used to irradiate for 20 s and 40 s at a microwave power of 60 kW,respectively.The surface damage extended 38 cm×30 cm and 53 cm×30 cm,respectively,and the damage extended to a depth of about 50 cm.The drilling speed was increased by 56.2%and 66.5%,respectively,compared to the case when microwaves were not used.