A Compact, Low-Power, and Electromagnetically Actuated Microspeaker for Hearing Aids

In this letter, we present an electromagnetically actuated microspeaker with microelectromechanical systems (MEMS) technology to reduce form factor, cost, and power consumption in hearing aid applications. The microspeaker has multilayer copper coils, a NiFe soft magnet on a polyimide membrane, and a NdFeB permanent magnet on the perimeter. The coil impedance is measured at 1.5 Omega and shows a very flat response across the audio frequency range. The device operates at a very low power, the lowest in MEMS speakers, comparable to that of the macro- size counterparts. A single-turn microspeaker with a diameter of 2.5 mm consumes 11.6 and 0.13 mW to generate a sound pressure level of 129 and 106 dB at 1 kHz, respectively. The measurement uncertainty is less than 10%, and the reproducibility is within 36% among the tested devices.     

Ic degradation behaviors of Bi-2223 superconducting tapes under axial fatigue loading

For the endurance evaluation of High Temperature Superconductors (HTS), the mechanical and transport properties of multifilamentary Bi₂Sr₂Ca₂Cu₃O_10+x (Bi-2223) superconducting tapes with different reinforcements subjected to high-cycle axial fatigue loading were investigated at 77 K in the self-field. The mechanical fatigue limits based on the relations between the applied stress amplitude and the numbers of cyclic steps to reach failure (S-N_f curves) were obtained. The transport properties were evaluated with the increase of repeated cycles, N, at different applied stress amplitudes which eventually leads to the electric fatigue limit. The influence of reinforcement on the mechanical and transport properties of Bi-2223 tapes were discussed. Fractographic observation was performed in order to understand the I_c degradation mechanism in fatigue tested Bi-2223 tapes.     

残余氧化硼对钛酸锶钡晶胞参数及相变温度的影响

研究了氧化硼掺杂（B2O3）烧结钛酸锶钡（Ba1-xSrxTiO3，x=0、0．4、1）陶瓷钙钛矿结构的稳定性、晶胞参数以及相变温度．结果表明，随着掺杂量的增加，钛酸锶钡仍保持原来的钙钛矿结构，但晶胞参数有所变化．晶格常数c与a并非单调变化，但轴比c／a单调递减而晶胞体积a^2c却单调增大．和未掺杂钛酸锶钡相比，掺杂钛酸锶钡陶瓷的相变温度有所升高．同一掺杂含量下，随着烧结温度的升高，因钛酸锶与钛酸钡相互固溶引起晶胞体积明显收缩，相变温度逐渐降低．但在同一烧结温度下，随着掺杂量的增加，相变温度几乎不变．说明硼离子半径虽然很小，氧化硼对钛酸锶钡晶胞参数的影响还是存在的，而且只能以填隙方式存在于晶胞，但其固溶能力非常有限．     

Comparison of Methods for Quantitation of Free Fatty Acids in Cheese

A comparison of three relatively rapid methods of determining free fatty acids concentrations in cheese was performed by correlating the results with a more laborious but accurate gas chromatographic (GC) technique. Acid Degree Values were found to correlate poorly with the GC data, particularly for short chain fatty acids. Values obtained using a Copper Soap Method correlated closely with the GC data for total and long chain fatty acids, but did not correlate as well with short chain fatty acids levels. The Extraction-Titration Method was found to be a simple and reliable technique that yielded values which correlate closely with short chain fatty acid concentrations.     

Improvement of machining quality of copper-plated roll mold by controlling temperature variation

Micro prism film used in LCD industry can be manufactured by roll to roll method with copper-plated roll mold. As copper-plated roll mold is getting larger, pitch error is getting severer. The pitch error drops the quality of micro prism film. The main cause of the pitch error was investigated during machining large roll mold whose machined length was 1 200 mm. The temperature of machining system was elevated during machining roll mold, and this elevation induced thermal expansion of the system. The temperature variation around the roll mold also made thermal expansion of the roll mold. The amount of thermal expansion had strong relationship to the amount of pitch error. Therefore, the roll mold was machined after warming-up of machining system and precise temperature controller around copper-plated roll mold was installed, which minimized the temperature variation. Finally, precise micro prism patterns without pitch error were machined on the large roll mold.     

EXTRACTION, FRACTIONATION AND ACTIVITY CHARACTERISTICS OF PROTEASES FROM SHRIMP PROCESSING DISCARDS

Proteases recovered from Northern pink shrimp (NPS) and Southern rough shrimp (SS) processing discards (heads, shells, tails) were characterized. Shrimp processing discards were extracted with water following homogenization and centrifugation in order to obtain the crude extract which was subsequently fractionated with solid ammonium sulfate. Two fractions sedimenting with 30–50% (designated as NPS‐I and SS‐I), and 50–70% (designated as NPS‐II and SS‐II) ammonium sulfate were collected following centrifugation, respectively. Endoprotease activity of the crude extract was 0.02 U/mg for hemoglobin (Hb, pH 3.0), 0.16 U/mg for azocasein (Ac, pH 6.0) and 0.12 U/mg for benzoyl‐Arg‐β‐naphthylamide (BANA, pH 7.0). The exoprotease activity was 0.11–0.17 U/mg for Arg‐β‐naphthylamide (ArgNA, pH 7.0), 0.06–0.11 U/mg for Lys‐β‐naphthylamide (LysNA, pH 7.0) and 0.08–0.09 U/mg for Leu‐β‐naphthylamide (LeuNA, pH 7.0). Endoprotease activity increased 5–7.4 fold for NPS‐I and SS‐I, and 1.9–2.7 fold for NPS‐II and SS‐II against crude extract. Meanwhile, exoprotease activity increased 3.6–4.8 fold for NPS‐I and SS‐I, and 5.6–7.2 fold for NPS‐II and SS‐II. Meat treated with NPS‐I and SS‐I was tenderized more extensively than that treated with NPS‐II and SS‐II. The results of this study suggest that proteases recovered from shrimp processing discards may potentially be used as processing aids in formulated foods.