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Effects of hydraulic retention time on net present value and performance in a membrane bioreactor treating

Dawei Yu, Jianxing Wang, Libin Zheng, Qianwen Sui, Hui Zhong, Meixue Cheng, Yuansong Wei

《环境科学与工程前沿（英文）》 2020年第14卷第6期 doi: 10.1007/s11783-020-1280-7

摘要： Abstract • The membrane bioreactor cost decreased by 38.2% by decreasing HRT from 72 h to 36 h. • Capital and operation costs contributed 62.1% and 37.9% to decreased costs. • The membrane bioreactor is 32.6% cheaper than the oxidation ditch for treatment. • The effluent COD also improved from 709.93±62.75 mg/L to 280±17.32 mg/L. • Further treatment also benefited from lower pretreatment investment. A cost sensitivity analysis was performed for an industrial membrane bioreactor to quantify the effects of hydraulic retention times and related operational parameters on cost. Different hydraulic retention times (72–24 h) were subjected to a flat-sheet membrane bioreactor updated from an existing 72 h oxidation ditch treating antibiotic production wastewater. Field experimental data from the membrane bioreactor, both full-scale (500 m3/d) and pilot (1.0 m3/d), were used to calculate the net present value (NPV), incorporating both capital expenditure (CAPEX) and operating expenditure. The results showed that the tank cost was estimated above membrane cost in the membrane bioreactor. The decreased hydraulic retention time from 72 to 36 h reduced the NPV by 38.2%, where capital expenditure contributed 24.2% more than operational expenditure. Tank construction cost was decisive in determining the net present value contributed 62.1% to the capital expenditure. The membrane bioreactor has the advantage of a longer lifespan flat-sheet membrane, while flux decline was tolerable. The antibiotics decreased to 1.87±0.33 mg/L in the MBR effluent. The upgrade to the membrane bioreactor also benefited further treatments by 10.1%–44.7% lower direct investment.

关键词： Antibiotic production wastewater Net present value Membrane bioreactor Hydraulic retention time Pollutant removal

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Carbon payments in the Guanzhong–Tianshui region to control land degradation

Zixiang ZHOU, Yufeng ZOU

《农业科学与工程前沿（英文）》 2017年第4卷第2期页码 246-253 doi: 10.15302/J-FASE-2017144

摘要： Carbon trading and carbon offset markets are potential policy options for mitigating greenhouse gas emissions and climate change. A price on carbon is expected to generate demand for carbon offsets. In a market-based framework, the carbon price should be high enough to compensate for opportunity costs. We studied a highly-modified agricultural system in the Guanzhong–Tianshui economic region of China that is typical of many temperate agricultural zones in western China. We quantified the economic returns from agriculture and from carbon plantings (both monoculture and ecological plantings) under five carbon-price scenarios. The mean carbon sequestration is 34 Mg·hm ·a , and the average annual payment increased to 1146 CNY·hm at a medium carbon price of 50 CNY·Mg CO . Thus, areas of high priority for conservation and restoration may be restored relatively cheaply in the presence of a carbon market. Overall, however, less carbon is sequestered by ecological plantings (i.e., mixed native trees and shrubs) compared to agriculture.

关键词： carbon-price carbon sequestration economic returns Guanzhong–Tianshui economic region net present value

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Research and industrialization of near-net rolling technology used in shaft parts

Zhenghuan HU, Baoyu WANG, Zhenhua ZHENG

《机械工程前沿（英文）》 2018年第13卷第1期页码 17-24 doi: 10.1007/s11465-018-0480-3

摘要：

Shaft part rolling is an efficient and green near-net shaping technology offering many advantages, including high production efficiency, high material utilization rate, high product quality, and excellent production environment. In this paper, the features of shaft part rolling are introduced along with the working principles of two main shaft part rolling technologies, namely, cross wedge rolling (CWR) and skew rolling (SR). In relation to this technology, some R&D achievements gained by the University of Science and Technology Beijing are summarized. Finally, the latest developments in shaft part rolling are presented, including SR steel balls, precise forming of camshaft blank by CWR, SR phosphorous copper balls at room temperature, and CWR hollow axle sleeve. Although the shaft part rolling technology has been widely used in China, it only accounts for about 15% of applicable parts at present. Nevertheless, this technology has broad application prospects.

关键词： cross wedge rolling skew rolling near-net rolling shaft part

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Renewable power for China: Past, present, and future

Eric MARTINOT

《能源前沿（英文）》 2010年第4卷第3期页码 287-294 doi: 10.1007/s11708-010-0120-z

摘要： This paper briefly examines the history, status, policy situation, development issues, and prospects for key renewable power technologies in China. The country has become a global leader in wind turbine and solar photovoltaic (PV) production, and leads the world in total power capacity from renewable energy. Policy frameworks have matured and evolved since the landmark 2005 Renewable Energy Law, updated in 2009. China’s 2020 renewable energy target is similar to that of the EU. However, China continues to face many challenges in technology development, grid-integration, and policy frameworks. These include training, research and development, wind turbine operating experience and performance, transmission constraints, grid interconnection time lags, resource assessments, power grid integration on large scales, and continued policy development and adjustment. Wind and solar PV targets for 2020 will likely be satisfied early, although domestic demand for solar PV remains weak and the pathways toward incorporating distributed and building-integrated solar PV are uncertain. Prospects for biomass power are limited by resource constraints. Other technologies such as concentrating solar thermal power, ocean energy, and electricity storage require greater attention.

关键词： renewable energy wind power solar power sustainable energy policy green industry

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The past, present and future of bovine pluripotent stem cells: a brief overview

Xiuchun TIAN

《农业科学与工程前沿（英文）》 2019年第6卷第1期页码 3-7 doi: 10.15302/J-FASE-2018247

摘要：

Although the pursuit of bovine embryonic stem cells started more than 26 years ago for the purpose of gene-targeting, true pluripotent stem cells in this economically important species are still elusive. With the rapid advances in genome-editing and cloning using homologously recombined somatic cells, the need for pluripotent stem cells for precise genetic modification in any species became questionable. With the pig being the better model for human regenerative biology, the identification of the commonalities and uniqueness of the pluripotency circuitry across mammalian species may be the main objective for studying pluripotent stem cells in the bovine.

关键词： bovine embryonic induced pluripotent stem cells

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Laparoscopic hepato-biliary-pancreatic surgery: present practices and prospects

Yongjun Chen, Renyi Qin, Xiaoping Chen

《医学前沿（英文）》 2011年第5卷第3期页码 235-238 doi: 10.1007/s11684-011-0156-4

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Co-present Pb(II) accelerates the oxidation of organic contaminants by permanganate: Role of Pb(III)

《环境科学与工程前沿（英文）》 2022年第16卷第8期 doi: 10.1007/s11783-022-1530-y

摘要：

• Simultaneous removal of organic contaminants and Pb(II) was achieved by Mn(VII).

关键词： Permanganate Pb(II) oxidation MnO₂ pH effect

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Basic research on machinery fault diagnostics: Past, present, and future trends

Xuefeng CHEN, Shibin WANG, Baijie QIAO, Qiang CHEN

《机械工程前沿（英文）》 2018年第13卷第2期页码 264-291 doi: 10.1007/s11465-018-0472-3

摘要：

Machinery fault diagnosis has progressed over the past decades with the evolution of machineries in terms of complexity and scale. High-value machineries require condition monitoring and fault diagnosis to guarantee their designed functions and performance throughout their lifetime. Research on machinery Fault diagnostics has grown rapidly in recent years. This paper attempts to summarize and review the recent R&D trends in the basic research field of machinery fault diagnosis in terms of four main aspects: Fault mechanism, sensor technique and signal acquisition, signal processing, and intelligent diagnostics. The review discusses the special contributions of Chinese scholars to machinery fault diagnostics. On the basis of the review of basic theory of machinery fault diagnosis and its practical applications in engineering, the paper concludes with a brief discussion on the future trends and challenges in machinery fault diagnosis.

关键词： fault diagnosis fault mechanism feature extraction signal processing intelligent diagnostics

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Special issue: Near-net shaping technology

Dequn LI, Dongming GUO, Qingxue HUANG, Yanchun LOU

《机械工程前沿（英文）》 2018年第13卷第1期页码 1-2 doi: 10.1007/s11465-018-0497-7

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IV) solvent extraction enhancement in high acidity using di-(2-ethylhexyl)phosphoric acid with [Cl] present

《化学科学与工程前沿（英文）》 2023年第17卷第1期页码 56-67 doi: 10.1007/s11705-022-2185-8

摘要： Separation of vanadium from black shale leaching solution at low pH is very meaningful, which can effectively avoid the generation of alkali neutralization slag and the resulting vanadium loss. In this study, coordination mechanism of vanadium in acid leaching solution at low pH was investigated with the intervention of chloride ions. Under the conditions of pH 0.8, di-(2-ethylhexyl)phosphoric acid concentration of 20%, phase ratio of 1:2, and extraction time of 8 min, the vanadium extraction could reach 80.00%. The Fourier transform infrared and electrospray ionization results reveal that, despite the fact that the chloride ion in the leachate could significantly promote vanadium extraction, the chloride ion does not enter the organic phase, indicating an intriguing phenomenon. Among Cl⁻–V, SO₄²⁻–V, and H₂O–V, the V–Cl bond is longer and the potential difference between coordinate ions and vanadium is smaller. Therefore, VO²⁺ gets easily desorbed with chloride ions and enter the organic phase. At the same time, the hydrogen ions of di-(2-ethylhexyl)phosphoric acid also enter the water phase more easily, which reduces the pH required for the extraction reaction.

关键词： vanadium black shale solvent extraction high acidity extraction

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Present situation and classification of piezoelectric pump

Fang YE, Shouyin WANG, Wei CHENG, Qixiao XIA, Jianhui ZHANG,

《机械工程前沿（英文）》 2009年第4卷第4期页码 420-429 doi: 10.1007/s11465-009-0052-7

摘要： According to the present classification method for a piezoelectric pump, this paper reviews the development and present situation of piezoelectric pumps in the latest 30 years and finally puts forward a new classification. A volumetric piezoelectric pump, which belongs to traditional volumetric pumps, can be divided into a piezoelectric pump with or without valves. A new valveless piezoelectric pump nowadays becomes a hot issue in scientific research. It is constructed by using no-moving-part valves, which can induce positive flow resistance and negative flow resistance different, and in which the inlet and outlet are connected all the time. New forms of piezoelectric pumps, different from traditional ones, are only at the stage of conception and principle, and no practical application has been reported.

关键词： piezoelectric pump development and present situation new classification method valveless piezoelectric pump new forms of piezoelectric pump

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基于时间-有色Petri网的电梯系统的建模与分析

宗群,窦立谦,程义菊

《中国工程科学》 2004年第6卷第12期页码 51-55

摘要：

根据时间Petri网和有色Petri网的知识，提出了基于时间-有色Petri网（TCPN）的电梯运行模型。依据此模型将电梯在每层的运行情况分类说明。电梯如何运行是由控制命令统一调度，控制命令是由与电梯运行状态相应的颜色集组成。最后举例说明此模型可在单台电梯控制系统和电梯群控系统中应用。

关键词： Petri网时间-有色Petri网电梯模型电梯运行

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Determining casting defects in near-net shape casting aluminum parts by computed tomography

Jiehua LI, Bernd OBERDORFER, Daniel HABE, Peter SCHUMACHER

《机械工程前沿（英文）》 2018年第13卷第1期页码 48-52 doi: 10.1007/s11465-018-0493-y

摘要：

Three types of near-net shape casting aluminum parts were investigated by computed tomography to determine casting defects and evaluate quality. The first, second, and third parts were produced by low-pressure die casting (Al-12Si-0.8Cu-0.5Fe-0.9Mg-0.7Ni-0.2Zn alloy), die casting (A356, Al-7Si-0.3Mg), and semi-solid casting (A356, Al-7Si-0.3Mg), respectively. Unlike die casting (second part), low-pressure die casting (first part) significantly reduced the formation of casting defects (i.e., porosity) due to its smooth filling and solidification under pressure. No significant casting defect was observed in the third part, and this absence of defects indicates that semi-solid casting could produce high-quality near-net shape casting aluminum parts. Moreover, casting defects were mostly distributed along the eutectic grain boundaries. This finding reveals that refinement of eutectic grains is necessary to optimize the distribution of casting defects and reduce their size. This investigation demonstrated that computed tomography is an efficient method to determine casting defects in near-net shape casting aluminum parts.

关键词： near-net shape casting aluminum parts casting defects low pressure die casting die casting semi-solid casting computed tomography

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Influence of damages on static behavior of single-layer cable net supported glass curtain wall: full-scale

Gang SHI, Yongjiu SHI, Yuanqing WANG, Yongzhi ZUO, Xiaohao SHI, Zaoyang GUO,

《结构与土木工程前沿（英文）》 2010年第4卷第3期页码 383-395 doi: 10.1007/s11709-010-0074-6

摘要： The single-layer cable net supported glass curtain wall has been applied in many building structures all over the world. In service, it will inevitably be subject to various damages. To study the influence of such damages on the static behavior of the single-layer cable net supported glass curtain wall, a full-scale model with the outside outline size of 4.85 m × 4.85 m and 4 × 4 grids is designed and tested. Two kinds of damages that are the cable prestress loss and cable anchorage end failure are led into the structure model during the test, and their influence has been investigated. The stiffness contribution of glass panels to the single-layer cable net supported glass curtain wall structure with or without damages and its change have been tested and analyzed. The results show that the maximum change rate of nodal deflection is 13.78% for the damage of cable prestress loss, while the change rate of nodal deflection is between 7% and 22% for the damage of cable anchorage end failure. The influence degree of the damages depends on the ratio of the structure initial stress stiffness change caused by damages to the total stiffness of the structure. The stiffness contribution of glass panels increases with the load increase. Under the same loading condition, the stiffness contribution of glass panels to the damaged structure is greater than that to the intact structure. The stiffness contribution of glass panels reduces the effect of the damages on the structural displacement and the cable tension force, but the glass panel could break if its stiffness contribution is too large.

关键词： single-layer plane cable net supported glass curtain wall damage cable prestress loss cable anchorage end failure stiffness contribution of glass panels

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中国低渗透油气的现状与未来

胡文瑞

《中国工程科学》 2009年第11卷第8期页码 29-37

摘要：

中国低渗透油气资源丰富，具有很大的勘探开发潜力。近20年来，在低渗透砂岩、海相碳酸盐岩、火山岩勘探方面取得了很大发现，形成了国际一流的开发配套技术，实现了低渗透油气藏的规模有效开发，低渗透油气产量持续上升，其在产量构成中所占比例逐年增加。无论从近几年新增探明储量还是从剩余油气资源量看，低渗透油气都是今后勘探开发的主要对象，低渗透油气是中国未来油气工业的勘探开发主流，对保障国家能源安全具有重要的战略意义。

关键词：低渗透油气勘探开发主流现状未来技术