Thermal stratification level of low sidewall air supply with air-conditioning system in large space

The thermal stratification level of low sidewall air supply system in large space was defined. Depending on the experiment of low sidewall air supply in summer 2008,the thermal stratification level was studied by simulation. Based on the simulation of experiment condition,the air velocity and vertical temperature distribution in a large space were simulated at different air-outlet velocities,and then the thermal stratification level line was obtained. The simulation results well match with the experimental ones and the average relative error is 3.4%. The thermal stratification level is heightened by increasing the air-outlet velocity with low sidewall air supply mode. It is concluded that when air-outlet velocity is 0.29 m/s,which is the experimental case,a uniform thermal environment in the higher occupied zone and a stable stratification level are formed. When the air-outlet velocity is low,such as 0.05 m/s,the thermal stratification level is too low and the air velocity is too small to meet the human thermal comfort in the occupied zone. So,it would be reasonable that the air-outlet velocity may be designed as 0.31 m/s if the height of the occupied zone is 2 m.

A Cosmic Microscope to Probe the Universe from Present to Cosmic Dawn:Dual-element Lowfrequency Space VLBI Observatory

A space-based Very Long Baseline Interferometry (VLBI) program, named as the Cosmic Microscope, is proposed to involve dual VLBI telescopes in the space working together with giant ground-based telescopes (e.g., Square Kilometre Array, FAST, Arecibo) to image the low radio frequency Universe with the purpose of unraveling the compact structure of cosmic constituents including supermassive black holes and binaries, pulsars, astronomical masers and the underlying source, and exoplanets amongst others. The operational frequency bands are 30, 74, 330 and 1670 MHz, supporting broad science areas. The mission plans to launch two 30-m-diameter radio telescopes into 2 000 km×90 000 km elliptical orbits. The two telescopes can work in flexibly diverse modes,(i) Space-ground VLBI. The maximum space-ground baseline length is about100 000 km; it provides a high-dynamic-range imaging capacity with unprecedented high resolutions at low frequencies (0.3 mas at 1.67 GHz and 20 mas at 30 MHz) enabling studies of exoplanets and supermassive black hole binaries (which emit nanoHz gravitational waves),(ii) Space-space single-baseline VLBI. This unique baseline enables the detection of flaring hydroxyl masers, and more precise position measurement of pulsars and radio transients at mas level.(iii) Single dish mode, where each telescope can be used to monitor transient bursts and rapidly trigger follow-up VLBI observations. The large space telescope will also contribute in measuring and constraining the total angular power spectrum from the Epoch of Reionization. In short, the Cosmic Microscope offers astronomers the opportunity to conduct novel, frontier science.

Microstrip Low-Pass Elliptic Filter Design Based on Implicit Space Mapping Optimization

It is a time-consuming and often iterative procedure to determine design parameters based on fine, accurate but expensive, models. To decrease the number of fine model evaluations, space mapping techniques may be employed. In this approach, it is assumed both fine model and coarse, fast but inaccurate, one are available. First, the coarse model is optimized to obtain design parameters satisfying design objectives. Next, auxiliary parameters are calibrated to match coarse and fine models’ responses. Then, the improved coarse model is re-optimized to obtain new design parameters. The design procedure is stopped when a satisfactory solution is reached. In this paper, an implicit space mapping method is used to design a microstrip low-pass elliptic filter. Simulation results show that only two fine model evaluations are sufficient to get satisfactory results.

基于CiteSpace的城市低碳社区研究分析

低碳城市是控制全球气候变暖的重要途径,而低碳社区建设是构建低碳城市的基础。文章借助CiteSpace软件工具梳理国内低碳社区的研究进展与实践进展,结合低碳理念发展的相关政策,研究发现国内低碳社区研究成果主要集中于空间规划、碳排放核算及建设机制三个方向,并对社区低碳化研究提出思考与建议:加强研究的针对性、统一低碳社区的研究概念与边界、建立低碳社区评估体系、构建社区单元碳排放发布机制。

A Perturbation Analysis of Low-Rank Matrix Recovery by Schatten p-Minimization

A number of previous papers have studied the problem of recovering low-rank matrices with noise, further combining the noisy and perturbed cases, we propose a nonconvex Schatten p-norm minimization method to deal with the recovery of fully perturbed low-rank matrices. By utilizing the p-null space property (p-NSP) and the p-restricted isometry property (p-RIP) of the matrix, sufficient conditions to ensure that the stable and accurate reconstruction for low-rank matrix in the case of full perturbation are derived, and two upper bound recovery error estimation ns are given. These estimations are characterized by two vital aspects, one involving the best r-approximation error and the other concerning the overall noise. Specifically, this paper obtains two new error upper bounds based on the fact that p-RIP and p-NSP are able to recover accurately and stably low-rank matrix, and to some extent improve the conditions corresponding to RIP.

SBIRS-low卫星红外探测系统探测距离分析

计算了SBIRS low卫星与弹头之间的空间距离及其星载红外探测器对弹头的最大理想探测距离,阐明了降低弹头表面温度以对抗(SBIRS low)卫星的有效性。

一种模拟非均匀介质中弹性波传播新的k-space方法

传统的伪谱(PS)方法,采用傅里叶变换(FT)计算空间导数具有很高的精度,每个波长仅需要两个采样点,而时间导数采用有限差分(FD)近似因而精度较低.当采用大时间步长时,由于时空精度不平衡,PS法存在不稳定性问题.原始的k-space方法可以有效地克服这些问题但是却无法适用于非均匀介质.为了提高原始k-space方法模拟非均匀介质波动方程的精度,我们提出了一种新的k-space算子族.它是用非均匀介质的变速度代替原k-space算子中的常数补偿速度构造得到,引入低秩近似可以高效求解.我们将构造的新的k-space算子应用于耦合的二阶位移波动方程,而不是交错网格一阶速度应力波动方程,使模拟弹性波的计算存储量减少.我们从数学上证明了基于二阶波动方程的k-space方法与基于一阶波动方程的k-space方法是等价的.数值模拟实验表明,与传统的PS、交错网格PS和原始的k-space方法相比,我们的新方法可以在时间和空间步长较大的均匀和非均匀介质中,为弹性波的传播提供更精确的数值解.在保持稳定性和精度的同时,采用较大的时空采样间隔,可以大大降低数值模拟的计算成本.

Low-carbon Concepts in the Planning of Residential Communities

It has become a common pursuit of designers to construct comfortable,energy-conserving,high-efficiency and natural living environment since the early 21st century.In the coming low-carbon age,the evolution of low-carbon concepts will surely bring positive influence on the present planning concepts of residential community,and meanwhile,propose higher requirements on the natural and ecological properties of residential community,such as its infrastructure construction,traffic organization,environment greening and so on.Through analyzing relevant concepts of low carbon,the authors studied the development of low-carbon concepts in "human-centered" designs,and its applications in architecture,traffic and green spaces.This study proposed that the improvement of low-carbon society could be started from the design of low-carbon residential communities,so as to satisfy the increasing ecological needs of people on living environment,and play a promotional role in facilitating the sustainable development of society.

LOW-REGULARITY SOLUTIONS TO FOKKER-PLANCK-TYPE SYSTEMS IN THE WHOLE SPACE

In this manuscript,we consider two kinds of the Fokker-Planck-type systems in the whole space.The first part involves proving the global existence and the algebraic time decay rates of the mild solutions to the Fokker-Planck-Boltzmann equation near Maxwellians if initial data satisfies some smallness in the function space L_(k)^(1)L_(T)^(∞)L_(v)^(2)∩L_(k)^(p)L_(T)^(∞)L_(v)^(2).The second part proves the global existence of the mild solutions to the Vlasov-Poisson-Fokker-Planck system in the function space L_(k)^(1)L_(T)^(∞)L_(v)^(2),and we also obtain the exponential time decay rates,which are different from the algebraic time decay rates of the Fokker-Planck-Boltzmann equation.Our analysis is based on Lk1LT∞Lv2function space introduced by Duan et al.(Comm Pure Appl Math,2021,74:932-1020),the L_(k)^(1)∩L_(k)^(p) approach developed by Duan et al.(SIAM J Math Anal,2024,56:762-800),and the coercivity property of the Fokker-Planck operator.However,it is worth pointing out that the L_(k)^(1)∩L_(k)^(p)approach is not required for the Vlasov-Poisson-Fokker-Planck system,due to the influence of the electric field term,which is different from the Fokker-Planck-Boltzmann equation in this paper and in the work of Duan et al.(SIAM J Math Anal,2024,56:762-800).

Baby space手卫生对极低出生体重儿医院感染的影响

目的观察新生儿重症监护室(NICU)中接触极低出生体重儿宝宝空间(Baby space)手卫生情况及研究期间医院感染率的变化。方法将2015年1月1日至2017年6月30日收住西安交通大学第二附属医院新生儿病区的极低出生体重儿按入院顺序分为对照组和观察组,对照组采用常规的手卫生规范;观察组在常规的手卫生规范基础上,对所有人员反复培训手卫生知识、床单元重点部位贴蓝色标识,蓝色标识区称为宝宝空间(Baby space),对观察结果进行分析。结果观察组手卫生依从性(90.4%)明显高于对照组(50.2%),差异有统计学意义(χ~2=327.314,P<0.05);观察组医院感染发生率(3.3%)明显低于对照组(13.3%),差异有统计学意义(χ~2=7.452,P<0.05)。结论为极低出生体重儿创造Baby space,在接触Baby space前后,严格执行手卫生规范,可提高手卫生依从性,从而能明显降低医院感染率。

Rebuilding of Traditional Riparian Spaces in Jiangnan:A Case Study of Conceptual Planning of Didang North Park in Shaoxing

Large-scale living spaces characterized with localization,nature,and vitality in Jiangnan area(Jiangnan refers to the southern regions of the Yangtze River) are gradually disappearing because of the extensive urbanization and modernization. In this paper,the suitable design method of riparian space is explored based on morphological features,composition principle,and spatial form of Jiangnan area,as well as the design philosophy of modern buildings. Besides,the conceptual planning of Didang Lake North Park in Shaoxing City is taken as a case study.

Reaction of water and living systems under the chronic effect of ionized radiation in low doses

It is represented the review about the effect of low doses of ionized radiation on different types of biological objects (Japanese quail embryos, Aspergillus niger, Spirostomum ambiguum Ehrbg., mezenchim stem cells of mice bone brain, dry seeds of the highest plants, blood lymphocytes of pilots and cosmonauts) and water medium. In model experiments under the chronic ionized radiation in doses comparable with the doses of ionized radiation inside the orbital space stations and during the flight in interplanetary space was shown alike with morphological deviations (Japanese quail embryos, Aspergillus niger), the phenomenon of radiation hormezis (Aspergillus niger, mezenchim stem cells), the increasing of the germination of seeds, the decreasing of spontaneous motion activity of spirostoms and DNA damage, chromosome aberrations and the increased radio-sensitivity to adding radiation load in blood lymphocytes. These data testified the fact that the definite factor of ionized radiation effect is the changing of water medium state. Thus under the interplanetary cosmic flight and long stay on the orbit in the region of magnetosphere the studying kinds of radiation first effected on the water medium of organism as a result morpho-functional structures were changed.

A PCA-Based Internet Delay Space Dividing Algorithm

It's a hot issue to improve the accuracy of network coordinate systems(NCS). By analyzing the error source of NCSes, it's emphasized that guaranteeing the low dimensionality of embedding datasets is the principle on the designing of NCSes. Based on this observation, a PCA based Internet delay space dividing algorithm(IDSD-PCA) is proposed. Beginning at choosing an optimized sub dataset randomly, IDSD-PCA partitions the Internet delay dataset into several sub datasets with low dimensionality by iterations. After the partition, the whole delay dataset and sub datasets are embedded into a hierarchical NCS. The experimental results show that with this framework both the metric space based models and the non-metric space based models can predict the end-to-end delays more accurately.

The micro structure of high carbon low alloy steel for easy drawing

For better processing performance of high carbon low alloy steel wire rod,an investigation about the influence of cementite lamellar spacing on wire 'easy drawing' performance is completed.It is pointed out that too thin cementite lamellar spacing(<80 um) reduces the strain hardening level of wire drawing, and reduce the torsion performance of drawn wire at same time.For the wire or wire rod from industrial production,compared with the micro-structure with troostite,the micro-structure with sorbite or sorbite mixed with pearlite is more suitable to the drawing process with high reduction ratio.

Study on Rational Well Spacing Optimization of Low Permeability Gas Reservoir

The Shanggu gas field is the low porosity and low permeability. Single well controlled reserves, economic limit well spacing and economic rational spacing through different methods are calculated. With the development experience of Su Lige gas field as guidance, the rational spacing of Shanggu gas reservoir is 700m×900m by calculating daily gas production rate and cumulative gas production with different well spacing using numerical simulation method.

土地出让市场化对城市碳排放绩效的影响研究--基于城市面板数据的检验分析

文章基于2011—2022年中国地级市的面板数据,测算地级市土地出让市场化水平与地级市碳排放绩效,采用空间面板模型、工具变量法及调节效应模型等实证方法,检验了土地出让市场化对城市碳排放绩效的影响及其内在机制。研究发现:土地出让市场化与城市碳排放绩效之间呈显著的“U”型非线性关系,且通过系列稳健性检验与内生性处理后,该结论依然成立;作用机制检验表明,资源配置与产业结构升级在土地出让市场化对城市碳排放绩效的作用机制中发挥中介作用;调节效应检验表明,双重目标约束在土地出让市场化与碳排放绩效关系中发挥显著调节作用。研究结论有助于深入理解土地出让市场化对城市碳排放绩效的影响效果和内在机理,为推进土地出让市场化发展、提升城市碳排放绩效和优化目标约束提供有益借鉴。

新发展阶段城市地下空间开发利用发展战略研究

作为城市建设和国土空间资源的重要组成部分,城市地下空间开发利用在新发展阶段的地位和作用愈显突出。本文通过剖析新发展阶段的新需求和新问题,提出了城市地下空间开发利用的新发展策略。基于国土空间规划新体系,绿色、低碳、韧性新理念以及土地存量更新的新模式等新发展阶段的特征和要求,分析了城市高质量发展对地下空间开发利用的战略需求;提出了新发展阶段城市地下空间开发利用需要解决的一系列新生问题,包括国土空间资源禀赋调查评价不足、承载能力概念不清,城市地下空间的绿色低碳韧性挖潜不充分,城市地下基础设施资源配置不均衡、发展机理机制不明确等。在此基础上,从治理体系建设、资源智慧管理、规划理论方法、数据驱动范式、深层空间利用、存量空间重构、新区一体化开发及地铁域控制等8个方面阐释了新发展阶段城市地下空间开发利用的重点任务和发展建议,以期为实现城市地下空间的立法为本、规划引领、建设有序和智慧管理提供有益借鉴。

子宫低级别子宫内膜样癌淋巴脉管间隙浸润的影响因素

目的探讨子宫低级别子宫内膜样癌患者淋巴脉管间隙浸润(lymphovascular space invasion,LVSI)的影响因素。方法回顾性分析2015年1月~2023年5月167例手术病理诊断低级别(G1、G2)子宫内膜样癌患者的临床资料。选择年龄、是否绝经、异常阴道出血时间、合并代谢综合征、CA125升高(≥35 U/ml)、子宫内膜厚度、宫腔占位、合并子宫腺肌症、国际妇产科联盟(International Federation of Gynecology and Obstetrics,FIGO)2009分期9项指标进行单因素分析,对P<0.05的因素进行二元logistic回归分析。结果167例子宫低级别子宫内膜样癌患者中,LVSI 24例(14.4%)。对单因素分析中P<0.05的4项因素(异常阴道出血时间≥4个月、CA125升高、合并子宫腺肌症、分期Ⅱ期及以上)进行二元logistic回归分析,结果显示分期Ⅱ期及以上(OR=7.357,95%CI:2.140~25.288,P=0.002),CA125升高(OR=4.883,95%CI:1.612~14.794,P=0.005)为子宫低级别子宫内膜样癌LVSI的独立预后因素。结论FIGO 2009分期Ⅱ期及以上、CA125≥35 U/ml与子宫低级别子宫内膜样癌患者LVSI有关,间接提示淋巴结转移风险,术前应高度关注,以便制定更为精准的手术方案。

低级别子宫内膜样癌患者淋巴脉管间隙浸润的危险因素分析及列线图预测模型构建

目的分析低级别子宫内膜样癌患者淋巴脉管间隙浸润(LVSI)的危险因素,构建列线图预测模型并评价其效能。方法收集2015年1月至2023年5月在首都医科大学附属北京友谊医院妇科进行初始治疗的167例低级别子宫内膜样癌患者的临床资料进行回顾性分析。根据脉管浸润情况将患者分为无脉管浸润组(143例)和脉管浸润组(24例)。运用Logistic回归分析法确定低级别子宫内膜样癌LVSI的危险因素。建立预测低级别子宫内膜样癌LVSI风险的列线图模型,使用一致性系数和校准曲线评估该模型的预测性能和符合度。结果采用多因素Logistic回归模型(逐步选择法)分析低级别子宫内膜样癌患者LVSI的独立危险因素,结果显示,阴道出血时间长、甘油三酯≥1.7 mmol/L,糖类抗原125≥35 kU/L,国际妇产科联盟临床分期Ⅱ期及以上是低级别子宫内膜样癌患者LVSI的独立危险因素(比值比=1.000、1.070、1.820、7.700,均P<0.05)。利用以上多因素Logistic回归分析筛选出的独立危险因素建立预测低级别子宫内膜样癌LVSI风险的列线图模型,经校准验证,预测风险接近于实际风险,一致性指数为0.843。结论临床高分期、血清高甘油三酯、高糖类抗原125和术前阴道出血时间长是低级别子宫内膜样癌患者LVSI的危险因素,利用这些指标构建的列线图模型可用于术前评估该类患者LVSI风险。