DAMAGE DETECTION BASED ON OPTIMIZED INCOMPLETE MODE SHAPE AND FREQUENCY

For the purpose of structural health monitoring, a damage detection method combined with optimum sensor placement is proposed in this paper. The back sequential sensor placement(BSSP) algorithm is introduced to optimize the sensor locations with the aim of maximizing the 2-norm of information matrix, since the EI method is not suitable for optimum sensor placement based on eigenvector sensitivity analysis. Structural damage detection is carried out based on the respective advantages of mode shape and frequency. The optimized incomplete mode shapes yielded from the optimal sensor locations are used to localize structural damage. After the potential damage elements have been preliminarily identified, an iteration scheme is adopted to estimate the damage extent of the potential damage elements based on the changes in the frequency. The effectiveness of this method is demonstrated using a numerical example of a 31-bar truss structure.     

Terminating surface electromigration at the source

Based on an extensive search across the periodic table utilizing first-principles density functional theory, we discover phosphorus to be an optimal surface electromigration inhibitor on the technologically important Cu(111) surface--the dominant diffusion pathway in modern nanoelectronics interconnects. Unrecognized thus far, such an inhibitor is characterized by energetically favoring (and binding strongly at) the kink sites of step edges. These properties are determined to generally reside in elements that form strong covalent bonds with substrate metal atoms. This finding sheds new light on the possibility of halting surface electromigration via kink blocking impurities.     

A study of phase separation of crystalline and miscible polymer blends. Poly(ε-caprolactone)/poly(styrene-co-acrylonitrile)

The phase separation of a crystalline and miscible polymer blend, poly(ε-caprolactone) /poly(styrene-co-acrylonitrile) (PCL/SAN), has been studied by differential scanning calorimetry (DSC), using a SAN containing 28.3% of acrylonitrile units. Several phenomena can be associated with the occurrence of phase separation depending upon the composition of the mixture. Following annealing at high temperatures, below and above the phase separation temperature T_c, three cases can be distinguished. In Case I, there is no sign of crystallization during quenching and DSC scanning, but a melting peak is observed at T_c, and above. In Case II, there is no crystallization on quenching but it does occur during the DSC run; the shift of the crystallization peak can then be related to T_c. In Case III, there is crystallization on quenching, and additional crystallization during the DSC run; the change of area of the crystallization peak is indicative of T_c. From these observations, the phase diagram of the system was determined. © 1993 John Wiley & Sons, Inc.     

Advances in Mechanical Properties of Hydrogels for Cartilage Tissue Defect Repair

Numerous factors, such as degeneration and accidents, frequently cause cartilage deterioration. Owing to the absence of blood vessels and nerves in cartilage tissue, the ability of cartilage tissue to heal itself after an injury is relatively low. Hydrogels are beneficial for cartilage tissue engineering owing to their cartilage-like structure and advantageous properties. Due to the disruption of its mechanical structure, the bearing capacity and shock absorption of cartilage are diminished. The tissue should possess excellent mechanical properties to ensure the efficacy of cartilage tissue repair. This paper discusses the application of hydrogels in the fields of cartilage repair, the mechanical properties of hydrogels used for cartilage repair, and the materials used for hydrogels in cartilage tissue engineering. In addition, the challenges faced by hydrogels and future research directions are discussed.     

New Class of Hydrido Iron(II) Compounds with cis‐Reactive Sites: Combination of Iron and Diphosphinodithio Ligand

The cationic complex [Fe(P₂S₂)(NCMe)₂]²⁺ (P₂S₂=(Ph₂PC₆H₄CH₂S)₂(C₂H₄) ([ 1 (NCMe)₂]²⁺)), with two MeCN ligands in a cis orientation, was synthesized and characterized. The MeCN ligand in [ 1 (NCMe)₂]²⁺ undergoes further substitution by a hydride ligand or CO to give iron(II) hydrides [H 1 (NCMe)]⁺, [H 1 H]⁰, and [H 1 (CO)]⁺. The order of reactivity of the hydrides was [H 1 H]⁰>[H 1 (NCMe)]⁺>[H 1 (CO)]⁺, and was illustrated by their reactions toward protic acids, the organic cation of 10‐methylacridinium (MeAcr⁺) as a hydride acceptor, and intermolecular hydride transfer reactions among these ferrous compounds. For example, MeAcr⁺ was reduced initially by a one‐electron transfer process from [H 1 H]⁰, resulting in competing reactions of MeAcr^. dimerization, hydrogen atom transfer from [H 1 H]⁺ to MeAcr^., and decomposition of [H 1 H]⁺. MeAcrH was produced in excellent yields through a single‐step H^? transfer from [H 1 (NCMe)]⁺ to MeAcr⁺, but [H 1 (CO)]⁺ was inactive toward MeAcr⁺.     

叶片型线对离心油泵性能的影响

以65Y60型离心油泵为研究对象，研究了液体不同粘度下叶片型线对泵性能的影响。首先，利用本课题组独立开发的准三元叶片设计程序以反问题方式设计了两种型线。这两种型线叶片前半部分与原一元叶轮叶片的型线不同、后半部分与一元叶轮相同。然后在不同粘度下将三个叶轮进行性能对比实验。研究表明，叶片进口附近的型线的改变对泵性能有较大影响；适当增大叶轮后盖板流面上的叶片流体动力负荷有助于提高离心油泵输送粘油时的水力性能。     

Cultivating <Emphasis Type="BoldItalic">Chlorella</Emphasis> sp. in a Pilot-Scale Photobioreactor Using Centrate Wastewater for Microalgae Biomass Production and Wastewater Nutrient Removal

This study is concerned with a novel mass microalgae production system which, for the first time, uses “centrate”, a concentrated wastewater stream, to produce microalgal biomass for energy production. Centrate contains a high level of nutrients that support algal growth. The objective of this study was to investigate the growth characteristics of a locally isolated microalgae strain Chlorella sp. in centrate and its ability to remove nutrients from centrate. A pilot-scale photobioreactor (PBR) was constructed at a local wastewater treatment plant. The system was tested under different harvesting rates and exogenous CO₂ levels with the local strain of Chlorella sp. Under low light conditions (25 μmol·m^-2s^-1) the system can produce 34.6 and 17.7 g·m^-2day^-1 biomass in terms of total suspended solids and volatile suspended solids, respectively. At a one fourth harvesting rate, reduction of chemical oxygen demand, total Kjeldahl nitrogen, and soluble total phosphorus were 70%, 61%, and 61%, respectively. The addition of CO₂ to the system did not exhibit a positive effect on biomass productivity or nutrient removal in centrate which is an organic carbon rich medium. The unique PBR system is highly scalable and provides a great opportunity for biomass production coupled with wastewater treatment.