Acoustic characterization and prediction for fan-duct-plenum-room integrations

This paper investigates mutual influence of duct and room acoustics in the whole fan-duct-plenum-room integrations. Applying the parametric design language of finite element software ANSYS (APDL), dimensional and positional influence on system acoustics has been studied. Models with different room dimensions, duct lengths, duct cross-sections, duct locations, duct discharges and duct elbow were constructed, and their characteristics were compared qualitatively. Results show that small rooms, short ducts, large duct cross-sections and bell mouth duct discharges help to increase room sound pressure levels (SPLs); SPLs in ducts and plenums are sensitive to duct dimensions and duct discharge types but insensitive to duct locations and room dimensions; duct elbows have relatively indistinct acoustic influence in each component. Based on the calculation results, a semi-experimental method was proposed for simply and approximately evaluating indoor acoustic spectra of fan-duct-plenum-room integrations, then an example was used to demonstrate the prediction process. Finally, by adopting several ideal models, sound field constitutions, duct and room wall admittances and duct end reflection were explored quantitatively. This study may give a detailed understanding of fan-duct-plenum-room acoustics for researchers, also it might provide a new, simple and approximate prediction method for professionals to evaluate and improve fan-ducted acoustics.     

The effect of construction material, contents and room geometry on the sound field in dwellings at low frequencies

An experimentally validated finite element method is used to model the sound level in rooms at low frequencies. It is demonstrated that the dimensions of rectangular rooms strongly influence the sound pressure level difference. Additional factors were investigated which are not normally considered in the frequency range where diffuse sound field conditions can be assumed. Three effects were investigated: room damping due to wall vibrations, furniture, the effect of small deviations from simple rectangular shapes. It is confirmed by field measurements that the vibrations of masonry walls and floors introduce less damping than surfaces of lightweight construction. Assigning to the FE model a damping equivalent to a surface absorption of 0.02 reproduces the effect of walls of heavyweight construction. Damping equivalent to a surface absorption of 0.15 reproduces the effects of plastered timber-frame walls, floors and ceilings. The work was briefly extended to a room pair built with heavyweight and lightweight material of construction. The modification of the shape of the room frequency response highlights well the effect of material of construction. In-situ and laboratory measurements show that furniture has little effect on steady-state room response below 100 Hz. Modelling a wall recess smaller than 0.5 m improved the agreement between prediction and measurements but the assumption of a simple rectangular room remains appropriate.     

高校计算机机房数据灾备研究

为了计算机机房数据能坚强支撑机房正常工作,基于对传统计算机机房数据的灾备方案的分析研究,和在网关服务器和客户机两个方面的实践经验,提出了一套有效的三层抵御新策略,并总结了其实际运行经验。     

固体基质室温燐光法测定L-色氨酸

本文提出在Na_2 CO_3存在下,以NaI为重原子微扰剂,以滤纸为基质的L-色氨酸的室温燐光(RTP)测定法。本法不需通干燥气体,工作曲线的线性范围较宽,用于谷物试样分析,得到了满意的结果。     

Synthesis of multi-hydroxyl and sulfonyl dual-functionalized room temperature ionic liquids

Starting from the hydroxylamine (dimethyl amino ethanol, triethanolamine) and 1,3-propane sultone, a series of hydroxyl and sulfonyl dual-functionalized zwitterionic salts and corresponding acidic room temperature ionic liquids have been synthesized. The hydroxyl groups of the synthesized substances were confirmed by the 1H NMR measurement. These zwitterionic salts and ionic liquids may be used for synthesizing other functionalized ionic liquids or ionic liquid-polymer (polyelectrolyte).     

以阴离子交换纤维素膜作基质室温燐光法测定痕量2,6-二氨基嘌呤的研究

本文对2,6-二氨基嘌呤(DAP)在不同的基质上和不同的重原子微扰剂存在下的室温燐光(RTP)强度进行比较,结果表明,NaI-NaAc是有效的重原子体系。适宜的固体基质为阴离子交换纤维素(二乙氨基乙基纤维素)膜(DEAE)和慢速定量滤纸。前者对酸度的变化具有较好的缓冲能力,本文提出了以DEAE为固体基质,测定痕量DAP的RTP法。     

Determination of ammonia based on the electro-oxidation of hydroquinone in dimethylformamide or in the room temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

The results detail a novel methodology for the electrochemical determination of ammonia based on its interaction with hydroquinone in DMF. It has been shown that ammonia reversibly removes protons from the hydroquinone molecules, thus facilitating the oxidative process with the emergence of a new wave at less positive potentials. The analytical utility of the proposed methodology has been examined with a linear range from 10 to 95 ppm and corresponding limit-of-detection of 4.2 ppm achievable. Finally, the response of hydroquinone in the presence of ammonia has been examined in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide, [EMIM][N(Tf)₂]. Analogous voltammetric waveshapes to that observed in DMF were obtained, thereby confirming the viability of the method in either DMF or [EMIM][N(Tf)₂] as solvent.     

Polypyrrole-Fe2O3 nanohybrid materials for electrochemical storage

We report on the synthesis and electrochemical characterization of nanohybrid polypyrrole (PPy) (PPy/Fe₂O₃) materials for electrochemical storage applications. We have shown that the incorporation of nanoparticles inside the PPy notably increases the charge storage capability in comparison to the “pure” conducting polymer. Incorporation of large anions, i.e., paratoluenesulfonate, allows a further improvement in the capacity. These charge storage modifications have been attributed to the morphology of the composite in which the particle sizes and the specific surface area are modified with the incorporation of nanoparticles. High capacity and stability have been obtained in PC/NEt₄BF₄ (at 20 mV/s), i.e., 47 mAh/g, with only a 3% charge loss after one thousand cyles. The kinetics of charge–discharge is also improved by the hybrid nanocomposite morphology modifications, which increase the rate of insertion–expulsion of counter anions in the bulk of the film. A room temperature ionic liquid such as imidazolium trifluoromethanesulfonimide seems to be a promising electrolyte because it further increases the capacity up to 53 mAh/g with a high stability during charge–discharge processes.     

Room‐Temperature Solution‐Processed PbS Quantum Dot Solar Cells

Colloidal quantum dots (CQDs) are attractive absorber materials for high‐efficiency photovoltaics because of their facile solution processing, bandgap tunability due to quantum confinement effect, and multi‐exciton generation. To date, all published performance records for PbS CQDs solar cells have been based on the conventional hot‐injection synthesis method. This method usually requires relatively strict conditions such as high temperature and the utility of expensive source material (pyrophoric bis(trimethylsilyl) sulfide (TMS‐S)), limiting the potential for large‐scale and low‐cost synthesis of PbS CQDs. Here we report a facile room‐temperature synthetic method to produce high‐quality PbS CQDs through inexpensive ionic source materials including Pb(NO₃)₂ and Na₂S in the presence of triethanolamine (TEA) as the stabilizing ligand. The PbS CQDs were successfully prepared with an average particle size of about 5 nm. Solar cells based on the as‐synthesized PbS CQDs show a preliminary power conversion efficiency of 1.82%. This room‐temperature and low‐cost synthesis of PbS CQDs will further benefit the development of solution‐processed CQD solar cells.