Period-doubling bifurcation in two-stage power factor correction converters using the method of incremental harmonic balance and Floquet theory

In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance （IHB） and Floquet theory. A two-stage power factor correction converter typically employs a cascade configuration of a pre-regulator boost power factor correction converter with average current mode control to achieve a near unity power factor and a tightly regulated post-regulator DC-DC Buck converter with voltage feedback control to regulate the output voltage. Based on the assumption that the tightly regulated postregulator DC-DC Buck converter is represented as a constant power sink and some other assumptions, the simplified model of the two-stage power factor correction converter is derived and its approximate periodic solution is calculated by the method of IHB. And then, the stability of the system is investigated by using Floquet theory and the stable boundaries are presented on the selected parameter spaces. Finally, some experimental results are given to confirm the effectiveness of the theoretical analysis.

Relationship among Teacher,Students and Teaching Material based on Balance Theory

Balance theory holds that when the subject is in the unbalanced state,there is two basic way to eliminate this situation.One is to change his attitude on the cognitive object;the other is to change the subject's attitude on reference person.To ex plain the relationship among teacher,students and teaching material by applying the Balance theory can help us find and solve problems during the education.It can generate motivation to restore a new balance to promote the development of education.

Research on adsorption mechanism of wall climbing robots based on internally balanced theory

The internally balanced theory proposed by the Japanese researchers,solved the contradiction between adsorption ability and moving capability of the permanent magnetic adsorption mechanism.However,it still has some problems when applied to wall climbing robots.This paper analyzes and improves this theory,and the improved internally balanced theory satisfies the requirements of the adsorption mechanism significantly.Finally,a practical prototype is proposed based on this method,and both the analysis using ANSYS and the experiment results justify the design validity.

Balance Theory and the Relationship among Teacher,Students and Teaching Material

The balance theory was supposed in 1950s,and it provides the theory basis for optimizing the classroom teaching.By applying this theory,we discuss how to keep balance among teacher,students and teaching material.This paper aims to keep these three factors in an open,dynamic and balanced system so as to guarantee the successful classroom teaching.

RENEWAL OF BASIC LAWS AND PRINCIPLES FOR POLAR CON-TINUUM THEORIES (Ⅱ)—MICROMORPHIC CONTINUUM THEORY AND COUPLE STRESS THEORY

The purpose is to reestablish the balance laws of momentum, angular momentum and energy and to derive the corresponding local and nonlocal balance equations for micromorphic continuum mechanics and couple stress theory. The desired results for micromorphic continuum mechanics and couple stress theory are naturally obtained via direct transitions and reductions from the coupled conservation law of energy for micropolar continuum theory, respectively. The basic balance laws and equations for micromorphic continuum mechanics and couple stress theory are constituted by combining these results derived here and the traditional conservation laws and equations of mass and microinertia and the entropy inequality. The incomplete degrees of the former related continuum theories are clarified. Finally, some special cases are conveniently derived.

Evaluation of a concept-based physical education unit for energy balance education

Background:Physical education(PE)is a key channel that impacts children's decisions and behaviors for healthful living.This study evaluated the effects of a concept-based PE(CBPE)instructional unit,featured by energy balance(EB)education,on students'knowledge learning,situational interest,cognitive,and physical engagements as well as teachers'perceptions.Methods:Fourth and 5th grade students(n=468)in a mid-western state of the United States were recruited as the participants.Four elementary schools were randomized to the CBPE or control groups.Students'EB knowledge,situational interest,cognitive engagement,and physical engagement were measured by a knowledge test,the Situational Interest Scale—Elementary,written task sheets,and accelerometers,respectively,while teachers'perceptions of the CBPE unit were captured by individual interviews at the end of the experiment.Results:The CBPE group showed a significant increase in EB knowledge,while the control did not.Both groups showed a similar increasing trend for situational interest over time,although the statistical results favored the control group.For physical engagement,the CBPE group demonstrated a statistically different but substantively similar level of in-class physical activity compared to the control group.The CBPE group also showed a moderate level of cognitive engagement throughout the unit.The PE teachers reported overall positive perceptions about teaching the CBPE unit.Conclusion:These results support the utility of the CBPE unit in enhancing EB education along with facilitating positive student interest and engagement as well as positive teaching experiences.

The Dao of Mathematical Creativity,Symmetry Theories,and Yin-Yang Philosophy With Their Classroom Applications

This paper introduces creativity,one of the significant features in maths.The creative mathematical beauty of symmetry and asymmetry are worth investigating in the practicing of Taichi.Symmetrical variances make the real world.Symmetry can be regarded as a kind of mirroring,like the line symmetry,the mirror image of the other parts,or rotational symmetry.Such characteristics can be vividly demonstrated in the traditional Chinese philosophical yin-yang theory(YY).The accompanying of male and female reveals the friendly cooperative relationship.YY reflects the counterparts of vacancy and firm,inhale and exhale,noun and verb,theory and practice,light and heavy,slow and fast,the pace,the sound effect in the classroom.Such an analysis is undergone about yin and yang in Yi School and Dao De Ching(DDC).Furthermore,there are detailed arguments of the symmetric nature of every verse of DDC,revealing the cultural value of the language.Their applications in the class admit the recognition under the new liberal arts project by China’s Ministry of Education.Yet,the integration of research and teaching is required to go further.

Gender Relations in Kjell Askildsen’s A Lovely Place From the Perspective of Chinese Yin-Yang Theory

A Lovely Place(2019)is a collection of the Norwegian writer Kjell Askildsen’s short stories that is translated from German into Chinese by Yang Zhizi.It contains 18 short stories,whose male characters are mainly analyzed by researchers.The paper argues that female characters are playing an indispensable role in compensating the males’life stories and enlightening their worldviews according to Chinese Yin-Yang theory.The females can be classified into the following three groups in terms of their important relations to the males.Firstly,the female is the male’s companion in a certain part of the latter’s life.Secondly,the female facilitates the male’s intellectual growth either spontaneously or purposefully.Thirdly,the female struggles for independence to set an example for the male.The female characters in A Lovely Place present such femininity as beauty,energy,nostalgia,sentimentality,motherhood,etc.,stimulate the males to reflect on their own identities and fulfill their muscularity,and function as the genuine protagonists in the collection as far as the gender relations are concerned.

How Confucian Philosophy of Balanced Harmony Promotes World Harmony

Harmony is the general principle for dealing with various social problems and promoting world harmony.China regards“harmony is most precious”as its ultimate value goal.Harmony is the core value and moral sentiment of the Chinese nation and it is the criterion for dealing with the relationships between people,between people and society,and between countries.The principles and methods of harmony should be used to govern a state so that it can be in a state of mutual integration.Harmony is a theoretical prescription for solving many crises and contradictions today.It is the meaning and value of learning and understanding universal rule.Harmony is the core value of the Chinese nation,the noumenon and universal rule of human existence,and the well-being of human existence.Harmony has various levels of expression,and its value is mainly reflected in harmony of oneself,harmony of the people,and harmony of nature.Benevolence is the core value concept of balanced harmony,and the philosophy of balanced harmony is realized through propriety.No matter for the communication between individuals,or the relationships between groups,nations,and countries,harmony is the eternal value pursuit and propriety is its eternal value carrier.

国家安全战略视域下的美国对华制度制衡及影响

形成于21世纪初的制度制衡理论,实际上已成为后冷战时期美国外交政策特别是对华政策的主导理论之一。从美国国家安全战略的角度,可以发现自2001年以来美国历届政府制约中国的因素不断上升,其对华实施的制度制衡方略经历了从包容性向排他性的转变。小布什政府采用试图将中国纳入美国主导的国际体系的包容性制度制衡方略,奥巴马政府则采用两面下注的混合型对华包容性制度制衡方略。特朗普政府主要利用美国国内法律和制度对华进行排他性制度制衡,而拜登政府采用“小圈子”对华进行排他性制度制衡。拜登政府在高科技领域对华实行制度制衡,企图在某种程度上迟滞中国高科技发展,客观上却促使中国自立自强形成尽可能完整的高科技生产链,对美国自身高科技产业和国内经济也产生“反噬”效应,无法从根本上改变经济全球化大趋势。

中医筋骨理论中筋与骨的关系内涵探讨

中医骨伤科学具有鲜明的特色,其中筋骨理论对指导临床具有重大的意义。筋骨理论是中医骨伤科学的经典理论,但筋骨理论散在记载于各经典中,筋与骨内涵关系尚未有系统的阐述,尤其是生理、病理、治疗原则上的关系均为零散阐述。本文综合文献认为筋骨理论筋与骨内涵关系主要表现在:生理上相辅相成,体现为筋骨和合、骨正筋柔、筋强骨壮、筋骨互用等;病理上相互影响,体现为筋弛骨痿、筋滞骨错、骨错筋挪、骨断筋离等;治疗上同辨同治,体现为:理筋正骨、筋骨并重、筋骨平衡、调衡筋骨、根源同治等。骨伤临床实践遵循筋骨理论的指导原则,无论内治或外治,均需要辨病辨证结合,同时“辨骨、辨筋”相结合。

视觉对人体姿势控制影响的脑功能网络连接机制

目的研究视觉对人体姿势控制影响及其脑功能网络连接机制。方法以15名健康青年为研究对象,要求受试者分别进行30 s睁眼、闭眼的双腿站立平衡,采集平衡过程中身体压力中心(center of pressure,COP)和脑电。对COP进行样本熵(SampleEn)计算;对脑电θ、α和β频段,计算相位滞后指数(phase lag index,PLI)构建大脑功能网络,并基于图论计算集聚系数(C)、特征路径长度(L)及小世界网络属性(σ)。结果人体在双腿站立平衡过程中,闭眼COPY样本熵显著高于睁眼(P<0.05)。闭眼α频段PLI平均值显著高于睁眼(P<0.05);闭眼α频段C、σ显著高于睁眼,L显著低于睁眼(P<0.05)。闭眼时α频段额区-中央区-顶区之间的网络连接以及中央区和顶区内连接强度显著高于睁眼(P<0.05)。闭眼时α频段PLI平均值以及C值与COPY样本熵中度呈中度负相关(P<0.05)。睁眼时左前额区、左顶区、左枕区α频段PLI平均值与COPY样本熵呈中度负相关;闭眼时左中央区、右枕区α频段PLI平均值则与COPY样本熵呈中度负相关。结论人体在站立平衡时,当没有视觉信息输入时,身体平衡稳定性下降,同时伴随着脑电α频段的脑网络连接增强以及大脑处理信息的效率需提升。人体在不同的视觉条件下进行姿势控制时,大脑会采用不同的神经策略。

无机化学中“酸碱解离”教学内容的重构探讨

依据素质教育中知识-能力-素质有机融合的思想指导,对《无机化学》酸碱解离内容进行重组,构建新的课程设计模块。内容重组扩充为5个模块,包括电解质溶液基础、酸碱理论概述、酸碱强度、弱酸弱碱解离平衡和酸碱滴定与误差基本概念。教学内容的重构在保证基本面知识结构完整的前提下与时俱进,从专业能力方面促进学生发展。

延伸斯金纳程序教学理论在病理生理学教学中的应用

斯金纳在程序性条件作用学说和强化理论基础之上创建了程序性教学法,该教学法是一种基于个性化学习的方法,有其独特的教学理论和原则。病理生理学是一门侧重于从代谢和功能变化角度研究疾病的病因、发病机制和转归的医学基础学科,其授课知识点之间逻辑性较强,不易理解。文章以病理生理学教学重点章节酸碱平衡紊乱为例,围绕学习目标要求,运用程序性教学法的理论和教学原则,设计酸碱平衡紊乱章节的程序性教学法的具体实施步骤,体现了程序性教学法的逻辑关联性强、自主性和层层递进式的学习特征,促进了学生对知识结构的梳理及对课程知识难点和重点的扎实掌握,探索了程序性教学法在病理生理学教学中应用的科学性和可操作性,为提高病理生理学教学效果提供可供参考的教学方法。

考虑时变线阻的多储能SOC稳定均衡控制策略

在直流微电网中,由于线路阻抗大小差异的复杂化,难以保证各储能单元之间达到荷电状态(state-of-charge,SOC)均衡。为此,提出一种考虑时变线阻的SOC均衡改进控制策略。首先,通过线路阻抗和SOC幂指数构造的平衡因子来修正控制系数,提高SOC的辨识度。同时,利用输出电流来约束平衡因子,提高系统的抗扰能力。在SOC均衡之后,SOC平衡因子G变为1,此时依赖线路阻抗信息但不受线路阻抗变化影响,可平稳地保持电流分配。并且结合输出电流构造的电压补偿环节有效地解决了母线电压质量和SOC均衡控制效果之间的矛盾。其次,针对基于SOC均衡的改进控制策略易受恒功率负载影响的问题,利用混合势函数理论进行建模,得到稳定性判据,有利于保障系统的稳定运行。最后,仿真结果表明,所提出的改进下垂控制能够有效地消除线路阻抗的影响,提高电流分配精度,实现SOC均衡,并验证了在各种突发扰动及极端情况下所提控制策略的有效性和正确性。

基于“筋骨平衡”理论针刺推拿疗法治疗椎动脉型颈椎病的临床观察

目的浅析椎动脉型颈椎病(cervical spondylotic vertebral arteriopathy,CSA)患者实施基于“筋骨平衡”理论针刺推拿疗法对其中医症状积分、颈性眩晕症状与功能评估量表(cervical vertigo symptom and function assessment scale,ESCV)评分、颈椎曲度及脑血流参数的影响。方法选择该院2019年12月—2021年12月就诊的CSA患者86例实施研究,随机数字表法分作观察组与对照组,各43例;其中对照组脱落2例,剔除1例,共完成40例;观察组脱落1例,剔除1例,共完成41例;对照组予以常规牵引疗法,观察组予以基于“筋骨平衡”理论针刺推拿疗法;比较两组治疗前与治疗后中医症状积分、ESCV评分、颈椎曲度及脑血流参数的变化,并对比两组疗效。结果治疗后,观察组中医症状积分皆显著低于对照组(P<0.05)。治疗后,观察组ESCV评分和颈椎曲度皆明显高于对照组(P<0.05)。治疗后,观察组椎底动脉及左、右椎动脉的Vs与Vd水平均显著高于对照组(P<0.05)。观察组总有效率显著高于对照组[95.12%(39/41)vs 80.00%(32/40),P<0.05]。结论基于“筋骨平衡”理论针刺推拿疗法对CSA患者疗效显著,有效改善中医症状积分、ESCV评分以及颈椎曲度,增强脑血流参数。

中国东部陆相断陷盆地页岩油开发理论认识与技术实践——以济阳页岩油为例

以济阳页岩油为代表的中国东部陆相断陷盆地页岩油取得产能突破,但埋藏深、厚度大、成熟度低,地层温度高、压力大,原油流动能力差的特点,使其实现高产稳产面临巨大挑战。基于万米岩心及90余口水平井生产实践,深化发展了“储-缝-压”三元储渗理论,以此为指导形成了页岩油开发甜点立体评价、立体开发优化设计、立体均衡压裂等济阳页岩油开发关键技术体系。理论研究和实践表明:孔隙和多尺度、多类型发育的微缝组成“双储”系统,控制着储集空间及油气富集规律,是高产稳产的物质基础;支撑缝与激活缝耦合形成跨纳米-厘米尺度的“双缝”系统,具有梯级启动特征,是高产稳产的渗流路径;地层保压性好的前提下,压裂增能可有效提高孔缝的渗流能力、增加渗吸置换效率,同时精细控压实现能场协同耦合,可进一步释放页岩油藏产能,保压增压“双压”协同是高产稳产的能量保障;以三元储渗理论为指导形成的开发关键技术体系为多洼陷多层系产能突破提供了有效的技术支撑,对促进中国东部陆相断陷盆地页岩油规模效益开发具有重要意义。

基于拉格朗日功能平衡法的单轨吊失速保护器触发理论分析

通过假设分步法从机器人学的角度对单轨吊机车失速保护器触发装置进行运动学分析,并对点位进行了详细描述。采用拉格朗日功能平衡法对失速保护器触发机构中的滑动轴位移状况建立了完整的动力学数学模型,通过该模型可以描述在运动过程中的滑动轴位移与运行速度、各部件参数之间的关系。借助Adams软件构建虚拟样机模型进行动力学仿真分析,得出所需的速度-位移仿真结果图。分析结果表明,滑动轴的位移与运行速度有关,当运行速度到达所设定临界值2 m/s时,滑动轴能够伸出足够长度以满足失速保护工作要求,符合数学模型的预期计算。

区分还是融合?虚拟化团队工作模式下的员工工作-家庭平衡策略

虚拟化团队工作模式成为当前企业运作的一个发展趋势,产生了无边界的工作特征,工作和家庭领域高度重叠,改变了以往工作和家庭可区分的研究和实践前提。为此,学者开始提倡顺应无边界的发展趋势,促进工作和家庭融合。然而,基于这一管理思路的企业实践却导致了一系列负面效果。这让我们不禁重新思考:在虚拟化团队工作模式发展趋势下,我们更适合采用以往的工作-家庭区分思路,还是当前的工作-家庭融合思路,抑或是其他新的管理思路?为解决这一重要问题,本研究通过社会认同理论弥补资源保存理论在解释力上的不足,探讨团队虚拟性如何影响员工的工作-家庭整合行为,采用怎样的管理思路进行有效的干预以达到工作和家庭和谐发展的效果。本研究为数智化变革下的工作-家庭平衡研究构建了新的理论框架,推动该领域理论的进一步发展,有助于指导企业从新的管理思路促进工作和家庭和谐发展。