Suchergebnisse

This paper gives a brief description of the over quick urbanization since Chongqing, one of the biggest cities in China, has been a municipality directly under the Central Government in 1997, excessive development and exceeding increase of high-rise buildings because of its special geographical position which finally leads to the worsening of the urban outdoor thermal environment. Then, this paper makes a bright balance to the field measurement and simulated results of the wind speed field, temperature field of one multifunctional high-rise building in Chongqing university located in the city center, and the contrasted results validate the correctness of CFD in the outdoor thermal environmental simulation, expose the disadvantages of high-rise buildings on the aspects of blocking the wind field, decreasing wind speed which results in accumulation of the air-conditioning heat revolving around and periscian region where sunshine can not rip into. Finally, in order to improve the urban outdoor thermal environment near the high-rise buildings especially for the angle of natural ventilation, this paper simulates the wind environment in different architectural compositions and architectural layouts by CFD, and the simulated results show that freestyle and tower buildings which can guarantee the wind speed and take the air-conditioning heat away are much suitable and reasonable for the special Chongqing geography. These conclusions can also be used as a reference in other mountain cities, especially for the one with a great number of populations.

We use in-situ heated nanoindentation to investigate the high-temperature nanomechanical properties of epitaxial and textured ZrB2 films deposited by magnetron sputtering. Epitaxial films deposited on 4H-SiC(0001) show a hardness decrease from 47 GPa at room temperature to 33 GPa at 600 °C, while the reduced elastic modulus does not change significantly. High resolution electron microscopy (HRTEM) with selected area electron diffraction of the indented area in a 0001-textured film reveals a retained continuous ZrB2 film and no sign of crystalline phase transformation, despite massive deformation of the Si substrate. HRTEM analysis supports the high elastic recovery of 96% in the films. ; Funding agencies: Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Swedish Research Council (VR) [621-2010-3921]

This study shows an approach to combine a high electrical conductivity of one composite layer with a high Seebeck coefficient of another composite layer in a double-layer composite, resulting in high thermoelectric power factor. Flexible double-layer-composites, made from Bi2Te3-based-alloy/polylactic acid (BTBA/PLA) composites and Ag/PLA composites, are synthesized by solution additive manufacturing. With the increase in Ag volume-ratio from 26.3% to 41.7% in Ag/PLA layers, the conductivity of the double-layer composites increases from 12 S cm(-1)to 1170 S cm(-1), while the Seebeck coefficient remains approximate to 80 mu V K(-1)at 300 K. With further increase in volume ratio of Ag until 45.6% in Ag/PLA composite layer, the electrical conductivity of the double-layer composites increases to 1710 S cm(-1), however, with a slight decrease of the Seebeck coefficient to 64 mu V K-1. The electrical conductivity and Seebeck coefficient vary only to a limited extent with the temperature. The high Seebeck coefficient is due to scattering of low energy charge carriers across compositionally graded interfaces. A power factor of 875 mu W m(-1) K(-2)is achieved at 360 K for 41.7 vol.% Ag in the Ag/PLA layers. Solution additive manufacturing can directly print this double-layer composite into intricate geometries, making this process is promising for large-scale fabrication of thermoelectric composites. ; Funding Agencies|Shanghai Innovation Action Plan Project [17090503600]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [11811530636, 61504081, 61611530550]; Program for Professor of Special Appointment (Young Eastern Scholar Program) at Shanghai Institutions of Higher Learning [QD2015039]; Swedish Research Council (VR)Swedish Research Council [2016-3365]; Swedish Energy AgencySwedish Energy Agency [46519-1]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

We demonstrate hydrothermal synthesis of coral-like CuO nanostructures by selective growth on ZnO nanorods (NR) at low temperatures. During the hydrothermal processing the resultant hydroxylated and eroded surface of ZnO NR becomes favorable for the CuO nanostructures growth via oriented attachments. Heterojunction p-n diodes fabricated from the CuO/ZnO nanocorals (NC) reveal stable and high rectification diode properties with a turn-on voltage ~1.52 V and negligible reverse current. The humidity sensing characteristics of the CuO/ZnO NC diodes exhibit a remarkable linear (in a semilogarithmic scale) decrease in the DC resistance by more than three orders when the relative humidity is changed from 30 – 90 %. The NC humidity sensor is also found to reveal the highest sensitivity factor ~6045 among available data for the constituent material's and a response and recovery time of 6 s and 7 s, respectively. ; funding agencies|Swedish government||

Background Quality of health care needs to be improved in rural China. The Chinese government, based on the 1999 Law on Physicians, started implementing the Rural Doctor Practice Regulation in 2004 to increase the percentage of certified physicians among village doctors. Special exam-targeted training for rural doctors therefore was launched as a national initiative. This study examined these rural doctors' perceptions of whether that training helps them pass the exam and whether it improves their skills. Methods Three counties were selected from the 4 counties in Changzhou City in eastern China, and 844 village doctors were surveyed by a questionnaire in July 2012. Chi-square test and Fisher exact test were used to identify differences of attitudes about the exam and training between the rural doctors and certified (assistant) doctors. Longitudinal annual statistics (1980–2014) of village doctors were further analyzed. Results Eight hundred and forty-four village doctors were asked to participate, and 837 (99.17%) responded. Only 14.93% of the respondents had received physician (assistant) certification. Only 49.45% of the village doctors thought that the areas tested by the certification exam were closely related to the healthcare needs of rural populations. The majority (86.19%) felt that the training program was "very helpful" or "helpful" for preparing for the exam. More than half the village doctors (61.46%) attended the "weekly school". The village doctors considered the most effective method of learning was "continuous training (40.36%)" . The majority of the rural doctors (89.91%) said they would be willing to participate in the training and 96.87% stated that they could afford to pay up to 2000 yuan for it. Conclusions The majority of village doctors in Changzhou City perceived that neither the certification exam nor the training for it are closely related to the actual healthcare needs of rural residents. Policies and programs should focus on providing exam-preparation training for selected rural doctors, reducing training expenditures, and utilizing web-based methods. The training focused on rural practice should be provided to all village doctors, even certified physicians. The government should also adjust the local licensing requirements to attract and recruit new village doctors.

Modern applications of refractory ceramic thin films, predominantly as wear-protective coatings on cutting tools and on components utilized in automotive engines, require a combination of excellent mechanical properties, thermal stability, and oxidation resistance. Conventional design approaches for transition metal nitride coatings with improved thermal and chemical stability are based on alloying with Al. It is well known that the solubility of Al in NaCl-structure transition metal nitrides is limited. Hence, the great challenge is to increase the Al concentration substantially while avoiding precipitation of the thermodynamically favored wurtzite-AlN phase, which is detrimental to mechanical properties. Here, we use VAlN as a model system to illustrate a new concept for the synthesis of metastable single-phase NaCl-structure thin films with the Al content far beyond solubility limits obtained with conventional plasma processes. This supersaturation is achieved by separating the film-forming species in time and energy domains through synchronization of the 70-mu s-long pulsed substrate bias with intense periodic fluxes of energetic Al+ metal ions during reactive hybrid high power impulse magnetron sputtering of the Al target and direct current magnetron sputtering of the V target in the Ar/N-2 gas mixture. Hereby, Al is subplanted into the cubic VN grains formed by the continuous flux of low-energy V neutrals. We show that Al subplantation enables an unprecedented 42% increase in metastable Al solubility limit in V1-xAlxN, from x-0.52 obtained with the conventional method to 0.75. The elastic modulus is 325 +/- 5GPa, in excellent agreement with density functional theory calculations, and approximately 50% higher than for corresponding films grown by dc magnetron sputtering. The extension of the presented strategy to other Al-ion-assisted vapor deposition methods or materials systems is straightforward, which opens up the way for producing supersaturated single-phase functional ceramic alloy thin films combining excellent mechanical properties with high oxidation resistance. Published by AIP Publishing. ; Funding Agencies|German Research Foundation (DFG) [SFB-TR 87]; VINN Excellence Center Functional Nanoscale Materials (FunMat) [2005-02666]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; Swedish Foundation for Strategic Research (SSF) [RIF14-0053]; Aforsk Foundation [16-359]; Knut and Alice Wallenberg Foundation [2011.0143]; JARA-HPC from RWTH Aachen University [JARA0131]

Dynamic ion-recoil mixing of near-film-surface atomic layers is commonly used to increase the metastable solubility limit x(max) in otherwise immiscible thin film systems during physical vapor deposition. Recently, Al subplantation achieved by irradiating the film growth surface with Al+ metal-ion flux was shown to result in an unprecedented x(max) for VAlN, far above values obtained with gas ion irradiation. However, it is reasonable to assume that ion irradiation necessary for subplantation also leads to a compressive stress sigma buildup. In order to separate the effects of Al+ bombardment on sigma and x(max), and realize low-stress high-x(max) nitride alloys, we grow metastable cubic V1-xAlxN (0.17 amp;lt;= x amp;lt;= 0.74) films using reactive magnetron sputtering under different ion irradiation conditions. Al and V targets are operated in Ar/N-2 discharges employing (i) conventional DC (Ar+, N-2(+)), (ii) hybrid High-power pulsed magnetron sputtering (HIPIMS)/DC processing with one type of metal ion present (Al+ or V+/V2+), and (iii) HIPIMS with concurrent Al+ and V+/V2+ fluxes. Comparison to the ab initio calculated Al solubility limit reveals that x(max) = 0.55 achieved with V+/V2+ irradiation is entirely accountable for by stress. In contrast, Al+ fluxes provide a substantial increase in x(max) to 0.63, which is 12% higher than that expected based on the stress-induced increase in metastable solubility. Correlative stress and atom probe tomography data confirm that the metastable Al solubility enhancement is enabled by Al+ subplantation. The here proposed processing strategy allows for growth of single-phase cubic nitride alloys with significantly increased Al concentrations embodying tremendous promise for substantial improvements in high temperature oxidation resistance and mitigates the risk of stress-induced adhesive or cohesive coating failure. Published by AIP Publishing. ; Funding Agencies|German Research Foundation (DFG) [SFB-TR 87]; VINN Excellence Center Functional Nanoscale Materials (FunMat) [2005-02666]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; Knut and Alice Wallenberg Foundation [2011.0143]; Aforsk Foundation [16-359]; JARA-HPC from RWTH Aachen University [JARA0151]

The first Fe-based MAX phase is realized by solid-state substitution reaction of an Fe/Au/Mo2GaC thin-film diffusion couple, as determined by X-ray diffraction and scanning transmission electron microscopy. Chemical analysis together with elemental mapping reveals that as much as 50 at.% Fe on the A site can be obtained by thermally induced Au and Fe substitution for Ga atomic layers in Mo2GaC. One-sixth of the original Ga is also replaced by Au atoms. When annealing Mo2GaC thin films covered with Fe only, the Mo2GaC phase remains intact, that is, Au acts as a catalyst for the substitution reaction. [GRAPHICS] . ; Funding Agencies|Swedish Foundation for Strategic Research (Stiftelsen for Strategisk Forskning, SSF) through the Synergy Grant FUNCASE; Knut and Alice Wallenberg (KAW) Foundation [KAW 2015.0043]; Swedish Research Council (Vetenskapsradet, VR) [621-2012-4425, 642-2013-8020, 2013-4018]; Swedish Government Strategic Research Area (SFO) [2009-00971]

We have deposited weakly textured substoichiometric NbB2-x thin films by magnetron sputtering from an NbB2 target. The films exhibit superhardness (42 +/- 4 GPa), previously only observed in overstoichiometric TiB2 thin films, and explained by a self-organized nanostructuring, where thin TiB2 columnar grains hinder nucleation and slip of dislocations and a B-rich tissue phase between the grains prevent grain-boundary sliding. The wide homogeneity range for the NbB2 phase allows a similar ultra-thin B-rich tissue phase to form between thin (5-10 nm) columnar NbB2-x grains also for films with a B/Nb atomic ratio of 1.8, as revealed here by analytical aberration-corrected scanning transmission electron microscopy. Furthermore, a coefficient of friction of 0.16 is measured for an NbB2-x film sliding against stainless steel with a wear rate of 5 x 10(-7) mm(3)/Nm. X-ray photoelectron spectroscopy results suggest that the low friction is due to the formation of a lubricating boric acid film. ; Funding Agencies|Vinnova (Swedish Governmental Agency for Innovation Systems) through the VINN Excellence Centre FunMat; Swedish Foundation of Strategic Research through the Synergy Grant FUNCASE; Knut and Alice Wallenberg Foundation

(Ti-0.5, Mg-0.5)N thin films were synthesized by reactive dc magnetron sputtering from elemental targets onto c-cut sapphire substrates. Characterization by theta-2 theta X-ray diffraction and pole figure measurements shows a rock-salt cubic structure with (111)-oriented growth and a twin-domain structure. The films exhibit an electrical resistivity of 150 m omega center dot cm, as measured by four-point-probe, and a Seebeck coefficient of -25 mu V/K. It is shown that high temperature (similar to 800 degrees C) annealing in a nitrogen atmosphere leads to the formation of a cubic LiTiO2-type superstructure as seen by high-resolution scanning transmission electron microscopy. The corresponding phase formation is possibly influenced by oxygen contamination present in the as-deposited films resulting in a cubic superstructure. Density functional theory calculations utilizing the generalized gradient approximation (GGA) functionals show that the LiTiO2-type TiMgN2 structure has a 0.07 eV direct bandgap. ; Funding Agencies|Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Knut and Alice Wallenberg foundationKnut & Alice Wallenberg Foundation [KAW-2020.0196, KAW-2018.0194]; Swedish Research Council (VR)Swedish Research Council [2016-03365, 2019-05403]; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research [FFL 15-0290]; Swedish Research CouncilSwedish Research Council [2018-05973]