| 1. |
- Xiong, Wenjuan, et al.
(author)
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SiNx films and membranes for photonic and MEMS applications
- 2020
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In: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 31, s. 90-97
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Journal article (peer-reviewed)abstract
- This work presents a novel process to form SiN x films and process for membranes with excellent mechanical properties for micro-electro-mechanical systems application as well as integration as IR waveguide for photonic application. The SiN x films were fabricated in SiNgen apparatus which is a single wafer chamber equipment compared to conventional low pressure chemical vapor deposition furnace process. The films showed low stress, good mechanical properties, but the synthesis also eradicates the issues of particle contamination. Through optimizing of the growth parameters and post annealing profile, low stress (40 Mpa) SiN x film could be finally deposited when annealing temperature rose up to 1150 °C. The stress relaxation is a result of more Si nano-crystalline which was formed during annealing, according to the FTIR results. The mechanical properties, Young’s modulus and hardness, were 210 Gpa and 20 Gpa respectively. For the waveguide application, a stack of three layers, SiO 2 /SiN x /SiO 2 was formed where the optimized layer thicknesses were used for minimum optical loss according to simulation feedback. After deposition of the first two layers in the stack, the samples were annealed in range of 900–1150 °C in order to release the stress. Chemical mechanical polish technique was applied to planarize the nitride layer prior to the oxide cladding layer. Such wafers can be used to bond to Si or Ge to manufacture advanced substrates.
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| 2. |
- Hao, Yanfen, et al.
(author)
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Air monitoring of polychlorinated biphenyls, polybrominated diphenyl ethers and organochlorine pesticides in West Antarctica during 2011-2017 : Concentrations, temporal trends and potential sources
- 2019
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In: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 249, s. 381-389
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Journal article (peer-reviewed)abstract
- Annual air samples were collected at various sites in the Fildes Peninsula, West Antarctica from December 2010 to January 2018 using XAD-2 resin passive air samplers to investigate concentrations, temporal trends and potential sources of persistent organic pollutants (POPs) in Antarctic air. Relatively low concentrations of polychlorinated biphenyls (PCBs) (Σ19PCBs: 1.5-29.7 pg/m3), polybrominated diphenyl ethers (PBDEs) (Σ12PBDEs: 0.2-2.9 pg/m3) and organochlorine pesticides (OCPs) (Σ13OCPs: 101-278 pg/m3) were found in the atmosphere of West Antarctica. PCB-11, BDE-47 and hexachlorobenzene (HCB) were the predominant compounds in the atmosphere. The concentrations of PCBs, HCHs, DDTs and endosulfans were found to show decreasing temporal trends, whereas uniform temporal trends were observed for HCB. The atmospheric half-life values for PCBs, HCHs, DDTs and endosulfans in Antarctic air were estimated for the first time, using regressions of the natural logarithm of the concentrations versus the number of years, obtaining the values of 2.0, 2.0, 2.4 and 1.2 year, respectively. An increasing ratio of α-HCH/γ-HCH indicated long residence time for α-HCH and possible transformation of γ-HCH to α-HCH in the atmosphere. The ratios of p,p'-DDT/p,p'-DDE were mostly lower than unity in this study, which could be attributed to aged sources. It was found that long-range atmospheric transport was still considered to be the main contributing factor to the atmospheric levels of the POPs in West Antarctica whereas the contribution of human activities at the Chinese Great Wall Station was minor. The results of this study give a view on the most recent temporal trends and provide new insights regarding the occurrence of various POPs in the Antarctic atmosphere.
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| 3. |
- Radamson, Henry H., et al.
(author)
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State of the Art and Future Perspectives in Advanced CMOS Technology
- 2020
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In: Nanomaterials. - : MDPI AG. - 2079-4991. ; 10:8
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Research review (peer-reviewed)abstract
- The international technology roadmap of semiconductors (ITRS) is approaching the historical end point and we observe that the semiconductor industry is driving complementary metal oxide semiconductor (CMOS) further towards unknown zones. Today's transistors with 3D structure and integrated advanced strain engineering differ radically from the original planar 2D ones due to the scaling down of the gate and source/drain regions according to Moore's law. This article presents a review of new architectures, simulation methods, and process technology for nano-scale transistors on the approach to the end of ITRS technology. The discussions cover innovative methods, challenges and difficulties in device processing, as well as new metrology techniques that may appear in the near future.
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| 4. |
- Zhou, Guoyi, et al.
(author)
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Climate and litter C/N ratio constrain soil organic carbon accumulation
- 2019
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In: National Science Review. - : Oxford University Press (OUP). - 2095-5138 .- 2053-714X. ; 6:4, s. 746-757
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Journal article (peer-reviewed)abstract
- Soil organic carbon (SOC) plays critical roles in stabilizing atmospheric CO2 concentration, but the mechanistic controls on the amount and distribution of SOC on global scales are not well understood. In turn, this has hampered the ability to model global C budgets and to find measures to mitigate climate change. Here, based on the data from a large field survey campaign with 2600 plots across China's forest ecosystems and a global collection of published data from forested land, we find that a low litter carbon-to-nitrogen ratio (C/N) and high wetness index (P/PET, precipitation-to-potential-evapotranspiration ratio) are the two factors that promote SOC accumulation, with only minor contributions of litter quantity and soil texture. The field survey data demonstrated that high plant diversity decreased litter C/N and thus indirectly promoted SOC accumulation by increasing the litter quality. We conclude that any changes in plant-community composition, plant-species richness and environmental factors that can reduce the litter C/N ratio, or climatic changes that increase wetness index, may promote SOC accumulation. The study provides a guideline for modeling the carbon cycle of various ecosystem scales and formulates the principle for land-based actions for mitigating the rising atmospheric CO2 concentration.
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| 5. |
- Akbari-Saatlu, Mehdi, et al.
(author)
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Silicon Nanowires for Gas Sensing : A Review
- 2020
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In: Nanomaterials. - : MDPI AG. - 2079-4991. ; 10:11
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Research review (peer-reviewed)abstract
- The unique electronic properties of semiconductor nanowires, in particular silicon nanowires (SiNWs), are attractive for the label-free, real-time, and sensitive detection of various gases. Therefore, over the past two decades, extensive efforts have been made to study the gas sensing function of NWs. This review article presents the recent developments related to the applications of SiNWs for gas sensing. The content begins with the two basic synthesis approaches (top-down and bottom-up) whereby the advantages and disadvantages of each approach have been discussed. Afterwards, the basic sensing mechanism of SiNWs for both resistor and field effect transistor designs have been briefly described whereby the sensitivity and selectivity to gases after different functionalization methods have been further presented. In the final words, the challenges and future opportunities of SiNWs for gas sensing have been discussed.
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| 6. |
- Bai, Xuan, et al.
(author)
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Sequential macrophage transition facilitates endogenous bone regeneration induced by Zn-doped porous microcrystalline bioactive glass
- 2021
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In: Journal of materials chemistry. B. - : Royal Society of Chemistry. - 2050-750X .- 2050-7518. ; 9:12, s. 2885-2898
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Journal article (peer-reviewed)abstract
- Macrophages play an important role in the immune microenvironment during bone healing, and sequential macrophage phenotypic transition could achieve superior osteogenic outcomes. Microcrystalline bioactive glasses (MCBGs) with osteoimmunomodulatory effects show potential in bone tissue regeneration. Zinc (Zn) has been approved to coordinate innate and adaptive immunity. Therefore, in this study, different amounts of ZnO were incorporated into microcrystalline bioactive glass to improve its immunomodulatory ability. The effect of Zn-MCBG ionic extracts on macrophage transition was studied, and the 5Zn-MCBG extracts could orchestrate sequential M1-to-M2 macrophage transition and promote the expression of proinflammatory and anti-inflammatory genes and cytokine expression to induce human bone marrow stromal cells (hBMSCs) osteogenic differentiation in vitro. Macroporous Zn-MCBG scaffolds containing mesopores were fabricated and showed good cell adhesion and feasible apatite formation when immersed in SBF in vitro. Furthermore, a rat calvarial defect model was used to confirm that the Zn-MCBG scaffold could modulate macrophage phenotypic transition and create a desirable osteogenic microenvironment to promote osteogenesis in vivo.
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| 7. |
- Ji, Yuanhui, et al.
(author)
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Thermodynamic analysis on the mineralization of trace organic contaminants with oxidants in advanced oxidation processes
- 2009
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:23, s. 10728-10733
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Journal article (peer-reviewed)abstract
- There is a growing demand for the efficient treatment of organic polluted wastewaters by advanced oxidation processes (AOPs) which calls for the determination of the mineralization order of ease for the organic contaminants with oxidants. The mineralization abilities of organic contaminants in AOPs are investigated in this work. Photocatalytic experiments for three representative organic contaminants are carried out, and their corresponding reaction rates are determined experimentally. Meanwhile, molar Gibbs free energy changes Delta(r)G(m)degrees for the reactions of 31 organic contaminants (10 chlorinated hydrocarbons, four brominated hydrocarbons, I I aromatic hydrocarbons and their derivatives, three chloroacetic acid, and three chloroacetyl chloride) with oxidants of (OH)-O-center dot, H2O2, O-center dot(-), O-3, and O-2 are calculated, and the mineralization order of ease is determined theoretically on the basis of Delta(r)G(m)degrees. The agreement of the theoretical and experimental mineralization abilities for most of the organic contaminants investigated implies the reliability of the determination of the mineralization ability from the magnitude of Delta(r)G(m)degrees for the mineralization of trace organic contaminants. Results also show that for most of the organic contaminants studied, the mineralization abilities are (OH)-O-center dot > H2O2 > O-center dot(-) > O-3 > O-2, and the mineralization ability of the organic contaminants depends on not only the oxidants but also the structure and properties of the organic contaminants themselves, and the degradation reaction products.
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| 8. |
- Li, Wenjuan, 1963-
(author)
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Firms and people in place : driving forces for regional growth
- 2007
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Doctoral thesis (other academic/artistic)abstract
- The aim of the thesis is to quantitatively study the driving forces and mechanisms for regional growth from an endogenous and exogenous perspective and reveal the most important factors contributing to regional growth, by focusing on three aspects: local labour market, the supply side and the demand side of the labour market. The thesis is designed to use Swedish micro register data to develop spatial models with higher spatial resolution. It was found that endogenous factors are important and probably explain about at least one third of total regional economic growth. Among the endogenous factors, localised demographic composition, labour force and labour market, firms, and business environment have the strongest influence on regional economic growth. The findings from the Swedish context were briefly compared to China’s economic growth in the last fifty years. The thesis consists of three related papers. The first paper studied the endogenous and exogenous factors in 108 Swedish LA regions during the 1990s. By using the SNI92 code, individual longitudinal data and an improved shift-share analysis method, it was found that the endogenous factor is important for regional economic growth because it is able to accelerate, decelerate or reverse the impact from exogenous factors during the period studied. The second paper studied regional growth from the supply side of the labour market by focusing on population redistribution and place attractiveness. A ‘floating grid’ approach was developed to understand the factors shaping place attractiveness. The approach disregards administration zones by focusing on a small spatial unit—vicinity which is one kilometre square. Each unit has a unique set of surrounding zones that are local area and hinterland. By constructing spatial models, the total explained variance in place attractiveness was decomposed into partial explanatory effects that are assigned for physical attraction, demographic, service and labour market factors over the spatial scales. The finding is that the spatial scale of vicinity and demographic factors contribute most to place attractiveness. The third paper studied regional growth from the demand side of the labour market by focusing on workplace and its economic performance. The ‘floating grid’ approach was once more applied while the basic analysis unit is a constructed workplace that holds working-square, local area and hinterland as surrounding zones. The economic performance of the workplace was attributed to external demand, local demand, business environment and labour force factors over different spatial scales. A method was developed to quantitatively identify intervals of partial explanatory effects that are components of the total explained variance. It was found that working-square and labour force factors contribute most to workplace economic performance.
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| 9. |
- Li, Wenjuan, 1963-, et al.
(author)
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Linking spatial scale to changes in workplace earnings : an exploratory approach
- 2015
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In: CyberGeo. - : Cybergeo. - 1278-3366.
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Journal article (peer-reviewed)abstract
- The paper investigates the importance of spatial scale for changes in earnings at the workplace by using spatial regression applied to workplace-level micro data in an exploratory purpose. A floating grid technique is used to define equal-sized workplaces and their daily-reach surrounding zones as divided into three spatial entities: working-square, local area and hinterland. On the basis of geo-referenced information on workplaces and places of residence along with numerous individual-level socio-economic indicators, the results of the regression models reveal that the indicators of the daily-reach area play a dominant role and that their contribution varies over spatial entities. Among the spatial entities, the working-square (km square) surrounding the workplace is more important than the workplace itself, the local area and the hinterland. Moreover, the results suggest that internal factors related to population size, diversity of trade and industry and educational level contribute to about one-third of changes in work income at the workplace level. It can be concluded that knowledge, learning and human capital are strongly associated with increased earnings.
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| 10. |
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