RESIDENCE TIME DISTRIBUTION STUDIES WITH TRACER EXPERIMENTS:IMPULSE INJECTION VERSUS STEP CHANGE OF FEED

1 INTRODUCTIONThe popularly used axial dispersion model is mathematically expressed by aone-dimensional partial differential

Direct Digital Frequency Control Based on the Phase Step Change Characteristic between Signals

We present a new digital phase lock technology to achieve the frequency control and transformation through high precision multi-cycle group synchronization between signals without the frequency transformation circuit. In the case of digital sampling, the passing zero point of the phase of the controlled signal has the phase step characteristic, the phase step of the passing zero point is monotonic continuous with high resolution in the phase lock process, and using the border effect of digital fuzzy area, the gate can synchronize with the two signals, the quantization error is reduced. This technique is quite different from the existing methods of frequency transformation and frequency synthesis, the phase change characteristic between the periodic signals with different nominal is used. The phase change has the periodic phenomenon, and it has the high resolution step value. With the application of the physical law, the noise is reduced because of simplifying frequency transformation circuits, and the phase is locked with high precision. The regular phase change between frequency signals is only used for frequency measurement, and the change has evident randomness, but this randomness is greatly reduced in frequency control, and the certainty of the process result is clear. The experiment shows that the short term frequency stability can reach 10-12/s orders of magnitude.

Runoff Responses to Climate Change in Arid Region of Northwestern China During 1960-2010

Based on runoff, air temperature, and precipitation data from 1960 to 2010, the effects of climate change on water resources in the arid region of the northwestern China were investigated. The long-term trends of hydroclimatic variables were studied by using both Mann-Kendall test and distributed-free cumulative sum (CUSUM) chart test. Results indicate that the mean annual air temperature increases significantly from 1960 to 2010. The annual precipitation exhibits an increasing trend, especially in the south slope of the Tianshan Mountains and the North Uygur Autonomous Region of Xinjiang in the study period. Step changes occur in 1988 in the mean annual air temperature time series and in 1991 in the precipitation time series. The runoff in different basins shows different trends, i.e., significantly increasing in the Kaidu River, the Aksu River and the Shule River, and decreasing in the Shiyang River. Correlation analysis reveals that the runoff in the North Xinjiang (i.e., the Weigan River, the Heihe River, and the Shiyang River) has a strong positive relationship with rainfall, while that in the south slope of the Tianshan Mountains, the middle section of the north slope of the Tianshan Mountains and the Shule River has a strong positive relationship with air temperature. The trends of runoff have strong negative correlations with glacier coverage and the proportion of glacier water in runoff. From the late 1980s, the climate has become warm and wet in the arid region of the northwestern China. The change in runoff is interacted with air temperature, precipitation and glacier coverage. The results show that streamflow in the arid region of the northwestern China is sensitive to climate change, which can be used as a reference for regional water resource assessment and management.

An improvement to the simulation of phase-change heat-transfer during soil freezing and thawing

A new variable time step method,which is called the backwards calculating time step method,is presented in this paper.It allows numerical simulation of soil freezing and thawing while avoiding "phase change missing and overflowing".A sensitive heat capacity model is introduced through which the calculation errors are analyzed.Then the equation using the self-adjusted time step is presented and solved using finite differences.Through this equation,the time needed for a space cell to reach the phase change point temperature is calculated.Using this time allows the time step to be adjusted so that errors caused by "phase change missing and overflowing" are successfully eliminated.Above all,the obvious features of this method are an accelerated rate for adjusting the time step and simplifing the computations.An actual example proves that this method can accurately calculate the temperature fields during soil freezing and thawing.It is an improvement over traditional methods and can be widely used on complicated multi-dimensional phase change problems.

Technology Demand Assessment of Adaption of Chinese Cities to Climate Change

Climate change adaptation is the process of preparing and actively adjusting to meet the climate change (negative effects and potential opportunities). Urban adaptation is aimed at the sensitivity level of risks and specific impacts of cities under the impact of climate change, and to develop policies and investment programs to reduce the vulnerability of cities to climate change risk. Urban adaptive action provides the basis and direction for the construction of urban resilience and sustainable development. Identifying the demand of adaption technologies, promoting the practical implementation of international technology transfer and reducing domestic emissions have important significance for the global response to climate change and improvement of the ability of urban adaptation. In this paper, through in-depth analysis on the concept and connotation of climate change, climate disasters and urban adaptation to climate change, the evaluation framework and steps of urban adaptation to climate change technology are determined, and six priority application technologies which can maximize the overall efficiency of sustainable development, improve the ability to adapt to climate change and at the same time reduce the cost at the greatest extent are identified.

How can collective leadership influence the implementation of change in health care?

Aim: This study focuses on how a collective leadership style could influence the implementation of change in health care.Methods: Kotter's 8-step process and leadership can guide the implementation of change. Collective leadership can highlight all levels of staff engagement, establish an organizational culture of learning and trust, and create continuous improvement. At the same time, it can formulate a well-designed plan;develop efficient strategies; communicate and empower the staff; assess the performance; and integrate the improvement.Results: Collective leadership can establish vision and trust, highlight all levels of staff engagement,establish an organizational culture of learning and trust, create continuous improvement, communicate and empower the staff and integrate the improvement.Conclusions: Collective leadership can be a powerful way to overcome the barrier and create an effective environment of adaptation of changes by analyzing Kotter's eight stage process.

How Should Mine Reclamation Design Effectively Respond to Climate Change? A Mini Review Opinion

Climate change is a growing concern with each of the last three decades being successively warmer than preceding decades. Mine wastes are mandatory required to be reclaimed after mine operation due to their high risks of contaminating environment and huge volumes occupying large useable land resources. However, most traditional mine reclamation plans are designed with an assumption of unchanged, consistent conditions of environment, climate and hydrology conditions, which may not work properly under the global climate change. This paper discussed the previously ignored problem that is how mine reclamation design should effectively respond to climate change. Through reviewing the current responding strategy to the climate change during mine reclamation and closure, this mini review was structured, and the opinion is concluded that the more active the designers consider the factors of climate change, the more manageable, predictable and sustainable the reclaimed ecosystem and landscape are. Nature-based solutions can act as the general guidelines when considering climate change with mine reclamation, and the six-step framework aims more specifically on mine reclamation. The two methods can work together to help designers and regulators to effectively respond to climate change when planning mine reclamation and closure.

基于Duncan-Chang模型的地基沉降分层总和分析方法探讨

地基沉降分析方法是土力学研究的重要内容。该文在地基沉降变形力学机理研究基础上,首先考虑埋深或初始地应力即先期固结应力对地基土变形模量的影响,并将其区分为初始地应力的体积应力和偏应力影响两部分,引进分级加载思想,建立出不同埋深地基土变形模量的确定方法;其次,将地基沉降区分为附加体积应力和附加偏应力引起的沉降两部分,建立出地基沉降分析计算模型;然后,考虑地基变形的非线性变化特征,引进增量分析方法、虎克定律和Duncan-Chang模型,建立出附加体积应力和附加偏应力引起的地基压缩层变形的分析方法,并利用地基沉降分层总和法分析原理,建立出基于Duncan-Chang模型的地基沉降分析新方法。该方法不仅可以反映初始地应力和附加应力对地基土变形模量的影响,而且,可避免地基土压缩试验曲线和地基静载试验曲线的使用;最后,通过工程实例计算与分析,并与实测沉降值和现有分析方法的计算结果进行比较,表明了该方法可以满足工程计算精度要求,具有一定的合理性与可行性。

两段阶梯加热成膜工艺对蛋白基复合材料疏水性和阻隔性能的影响

目的:改良成膜加热工艺。方法:将薄膜基材采用一段35,40,45,50,55℃低温解链,二段85℃变性加热的方法制备乳清分离蛋白—普鲁兰多糖薄膜。研究比较了薄膜结构、疏水性、阻隔性能和力学性能的变化,确定了优化成膜工艺条件。结果:两段阶梯加热的薄膜对比未变性交联(25℃)的薄膜和一段加热(85℃)的薄膜,阻氧性能提高了25.0%~58.7%,拉伸强度(TS)增强了54.8%~89.9%,断裂伸长率(EAB)增强了40.2%~59.2%,水蒸气阻隔性能提高了20.0%~52.6%。结论:两段阶梯加热的成膜方式能控制蛋白质解链程度,促进成膜基材基团之间的反应且45℃/85℃加热条件对提高薄膜各项性能的作用最为显著。

基于STEP的CAD/CAM系统产品数据交换研究

主要论述了CAD/CAM系统中产品数据表达与交换的重要性,介绍了产品数据表达与交换标准STEP的产生与发展、文件内容以及STEP的体系结构和组成,给出STEP应用实例。

城市内涝灾害对应急救援服务可达性的影响评估

【目的】城市化进程加快和气候变化导致内涝积水频发,造成道路封闭和交通堵塞,给城市应急救援响应的时效性带来严重影响。为了准确评估暴雨内涝下的城市应急救援响应能力,【方法】以荔湾区为例,通过构建内涝水动力模型,模拟不同设计降雨情景下的内涝积水,识别道路积水风险,明确阻断道路,并结合两步移动搜寻法(2SFCA)对不同脆弱性的兴趣点(POI)的应急救援服务可达性进行评估。【结果】结果显示:随着降雨重现期从1 a一遇增大到100 a一遇,内涝积水面积增大,平均积水深度从0.08 m增大到0.20 m。受积水影响道路数量持续增加,阻断道路长度从11 km上升至49 km,增长了超过300%。随着阻断道路的增多,应急救援可达的POI数量呈现下降趋势,并且在不同时间阈值内平均下降40%以上,可达性呈明显下降趋势。【结论】内涝模型耦合城市路网得到的道路积水可以揭示阻断道路的总体格局,可达性模型可以快速估算出应急救援的时效性。结果可为应急救援响应能力的评估提供参考。

酿酒葡萄“厂”形四步整形技术及应用效果调查

西北地区的葡萄栽培中,秋季的埋土防寒是必要环节,因此适宜的整形技术是保证葡萄酒产业可持续发展的重要措施。文章以‘赤霞珠’和‘马瑟兰’等主要酿酒品种为对象,根据多年实践经验总结出了“厂”形的四步整形技术:一年培育壮苗,二年培育壮蔓,三年上架结果,四年基本成形。通过调查各品种幼龄树的生长发育情况发现,栽植第一年多数品种的新梢在秋季的成熟芽眼数达到10个以上,但第二年‘赤霞珠’‘美乐’‘马瑟兰’3品种的长势较好,其它品种长势较差;对产量和品质的调查发现,各品种四年生树的产量较低,并以‘赤霞珠’和‘马瑟兰’品种表现较好,分别达到十年生树的78.19%和68.65%;而果实品质与十年生树无明显差异。综上所述,“厂”形树形适用于西北埋土防寒区酿酒葡萄栽培。

行为改变理论构建中年急性胰腺炎患者阶梯式饮食干预策略及应用

目的 通过行为改变理论构建阶梯式饮食干预策略,并探讨其在中年急性胰腺炎患者中的应用效果。方法 采用前瞻性随机对照研究,选择2020年5月至2022年5月北京友谊医院感染内科收治的80例中年急性胰腺炎患者作为研究对象,经随机数字表法分为对照组与观察组,每组40例。对照组采用阶梯式饮食干预策略,观察组采用行为改变理论构建的阶梯式饮食干预策略。比较2组护理前后的营养指标[血清总蛋白(TP)、白蛋白(ALB)、血红蛋白(Hb)]、健康行为[健康促进生活方式量表-Ⅱ(HPLP-Ⅱ评分)]、生活质量[生活质量评价量表(SF-36评分)]以及护理满意度。结果 观察组患者护理后TP、ALB、Hb均显著高于同期对照组(P<0.05);与对照组比较,观察组患者遵医嘱、自我监测、定期复查、控制饮食的占比更高(P<0.05)。观察组患者护理后HPLP-Ⅱ评分显著高于同期对照组(P<0.05);观察组患者护理后SF-36评分、ADL评分显著高于同期对照组(P<0.05);与对照组比较,观察组患者不良事件发生率更低,护理满意度更高(P<0.05)。结论 中年急性胰腺炎患者采用行为改变理论构建的阶梯式饮食干预策略可以改善机体营养状态,提高自我管理、健康行为及生活质量水平,不良事件发生率更低,患者满意度更高。

温度突变下人体热反应的实验研究

利用人工气候室模拟了不同季节对应的9种温度突变工况,对24名受试者开展了中性→热(冷)→中性往返式温度突变对人体热反应影响的实验研究,得到了环境温度发生突变时人体生理反应、主观反应及全身热负荷的变化规律。研究发现:在各突变工况下,主观反应变化超前于生理反应变化;突变前后人体生理和心理反应出现不对称现象;在热→中性突变工况下人体出现“冷感超越”,通过分析实验过程中人体各项散热量的变化规律,发现“冷感超越”的原因是皮肤蒸发散热量显著增大进而导致人体总散热量远大于产热量。温度突变动态环境中的热感觉与平均皮肤温度及其变化率均呈线性关系,得到了基于皮肤温度的热感觉预测模型。将人体热负荷及其变化量引入热感觉预测模型中,得到了基于热负荷的热感觉预测模型。PMV模型、基于皮肤温度的热感觉预测模型、基于热负荷的热感觉预测模型的对比显示,基于热负荷的预测模型能够更好地预测温度突变环境下的人体热感觉。

基于COMSOL分析步进电动机故障的电流和磁场变化规律研究

步进电动机是电力系统稳定运行的关键设备之一,当步进电动机在运行过程中出现故障,将直接导致电力系统的停运,给电力企业带来经济损失,需要对步进电动机内部故障原因进行研究。通过COMSOL有限元分析及建模的方式,对步进电动机的失步故障和开路故障所引起的电场和磁场的变化展开了研究,分析了在5种不同频率下失步故障和开路故障所引起的电场和磁场的变化规律,以提高对步进电动机故障诊断的效率。

新质生产力的概念、内涵与体系:以“创新”促“质变”

自从习近平总书记提出新质生产力以来,学术界对新质生产力的概念、意义、作用等开展了多角度的诠释、解读和分析。本文从新质生产力质变特征的“阶跃式升级”“要素组合升级”两个视角,理论联系实际,从供给侧分析了新质生产力的内涵及其在以高质量发展推进中国现代化进程中的重大意义和作用。具体来看,首先,本文基于马克思主义视域剖析了新质生产力的概念。其次,深入分析了新质生产力质变特征的“阶跃式升级”“要素组合升级”内涵。再次,深入剖析了发展新质生产力的动力机理和内在逻辑,提出发展新质生产力的关键是科技创新,核心是制度创新,充分发挥数据要素和管理要素的作用。最后,重点强调了以“创新”促“质变”发展新质生产力,需要解放思想、实事求是。

数字经济背景下企业信用管理的数字化变革

数字经济的发展离不开信用机制的支撑。数字经济时代,企业信用管理数字化是企业参与数字经济建设、应对信用监管的必然要求,是加强企业经营能力、提升信用管控能力的迫切需要。在信用管理数字化过程中,企业面临信用管理体系不完善、信用管理意识薄弱、缺乏信用管理沟通机制、信息化发展滞后、数字化进程缓慢等问题。建议企业信用管理数字化实施“一三五步走”发展战略,即构建贯穿事前事中事后的全链条数字化信用管理机制,达到全业务覆盖、全链条控制、全过程跟踪,实现对企业信用风险的闭环管控。

相变储能材料六水氯化钙的储热性能优化研究

六水氯化钙(CaCl_(2)·6H_(2)O)的相变温度约为29℃,相变潜热约180.0~190.8 J/g,因其潜热高,成本低,无毒等优点广泛应用于建筑材料中,但CaCl_(2)·6H_(2)O在实际应用中存在着储热性能差、衰减严重等缺点。通过差示扫描量热法(DSC)、原子力显微镜(AFM)、X射线衍射法(XRD)对比了CaCl_(2)·6H_(2)O在改性前后的潜热性能、形貌及晶体结构差异。结果表明,通过对CaCl_(2)·6H_(2)O的水含量进行精确调控,材料的相变潜热从158.6 J/g提升至194.8 J/g,潜热存储能力得到极大的提升。