Thermal degradation of poly[3-dimethyl(methylmethacryloylethyl) ammonium propanesulfonate]

The thermal degradation of poly[3-dimethyl (methylmethacryloyl)ammonium propanesulfonate], [poly(DMAPS)], was studied under nitrogen and air atmosphere at various heating rates. The kinetic parameters such as activation energy, preexponential factor, and reaction order were determined by Ozawa's method. Thermal degradation of such polymer occurs in two and three stages in nitrogen and air atmosphere, respectively. Larger sample weights produce a larger temperature interval (ΔT), but the weight loss (ΔW) between the temperature of the start and the end of degradation is approximately independent of the sample weights.     

Fast-searching algorithm for vector quantization using projection and triangular inequality

In this paper, a new and fast-searching algorithm for vector quantization is presented. Two inequalities, one used for terminating the searching process and the other used to delete impossible codewords, are presented to reduce the distortion computations. Our algorithm makes use of a vector's features (mean value, edge strength, and texture strength) to reject many unlikely codewords that cannot be rejected by other available approaches. Experimental results show that our algorithm is superior to other algorithms in terms of computing time and the number of distortion calculations. Compared with available approaches, our method can reduce the computing time and the number of distortion computations significantly. Compared with the best method of reducing distortion computation, our algorithm can further reduce the number of distortion calculations by 29% to 58.4%. Compared with the best encoding algorithm for vector quantization, our approach also further reduces the computing time by 8% to 47.7%.     

Characterization of fluid distributions in porous media by NMR techniques

Nuclear magnetic resonance (NMR) spin-lattice relaxation measurements are used to investigate pore structures and fluid phase distributions in porous media. A new method for estimating relaxation time distribution functions from measured relaxation data is presented using a B-spline basis to represent the distribution function and Tikhonov regularization to stabilize the estimation problem. Surface relaxivity, which is required to convert relaxation time distributions to pore-size distributions of fluid phase distributions at partial saturations, is determined using pore volume-to-surface-area ratios estimated by NMR diffusion measurements. This approach was validated by analyzing certain model porous media with known pore volume-to-surface-area ratios. The method is demonstrated by determining pore-size and fluid phase distributions of sandstone and carbonate samples, as well as by comparing the pore-size distributions of chalk samples obtained by this methodology with those estimated by mercury porosimetry.     

Primary small-intestinal lymphomas in Taiwan: immunoproliferative small-intestinal disease and nonimmunoproliferative small-intestinal disease

PURPOSE: The clinicopathologic findings in 45 adult Chinese patients with primary small-intestinal lymphoma (PSIL) are described and compared with those in Western countries and in underdeveloped nations. The efficacy of combination chemotherapy is also assessed. PATIENTS AND METHOD: Six patients had immunoproliferative small-intestinal disease (IPSID) indicated by the presence of alpha-heavy chain protein (alpha-CP) in body fluids or tumor tissues. Thirty-nine patients had non-IPSID, including one with postrenal transplant lymphoma. Thirty-three non-IPSID patients received a minimum of four cycles of combination chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisolone (CHOP). RESULTS: All IPSID patients presented with the clinical and laboratory features of severe intestinal malabsorption, and all had diffuse lymphoplasmacytic infiltration in the mucosa of the small bowel. Lymphomas were localized mainly in the jejunum and mesenteric nodes. The histologic subtypes were diffuse large cell in two, immunoblastic in three, and diffuse mixed in one. All patients responded poorly to chemotherapy, with a median survival duration of 10.5 months. The common presenting symptoms of the 39 non-IPSID patients included abdominal pain (90%), weight loss (31%), abdominal mass (26%), obstruction (26%), and perforation (23%). Diffuse large-cell and immunoblastic lymphomas constituted 82% of cases. Four patients had stage IE, 19 stage II 1E, and 16 stage 112E disease according to the Musshoff's criteria; 22 had bulky tumors and 19 had multiple tumors. The tumors were completely resected in 14 patients. Of 33 patients treated with combination chemotherapy, 73% achieved a complete remission. With a median follow-up duration of 90 months, there have been four relapses, with only one at the primary tumor site. The overall 5-year survival and disease-free survival rates for non-IPSID patients who were treated with chemotherapy were 59% and 54%, respectively. CONCLUSION: Intensive chemotherapy produces long-term disease-free survival in locally advanced non-IPSID PSIL.     

The design, analysis, and development of highly manufacturable 6-T SRAM bitcells for SoC applications

We present here an extensive static random access memory (SRAM) bitcell development methodology that has led to the qualification and production of the smallest 6-T SRAM bitcell reported in 0.13-/spl mu/m CMOS technology. No additional processing steps were employed in accomplishing this result. Such a methodology is being extended also to subsequent technology generations. The development efforts included the electrical evaluation of several candidate 6-T SRAM bitcell architectures for both high-density and high-speed applications. Based on the electrical evaluations, the chosen cell architectures were incorporated in silicon and verified for their robustness with respect to critical design rules, yields and reliability. The methodology for optical proximity correction for bitcell development has been described here. Minor process enhancements to ensure compatibility of the overall process flow with the SRAM bitcells are described. The use of SRAM-specific electrical test structures serves an important role in validating the electrical performance and confirming the robustness of the bitcells in a manufacturing environment. The monitoring of V/sub ddmin/, the minimum voltage at which the memory is functional was used to drive overall process improvements and reliability. Lastly, measurements of soft error rates demonstrated excellent immunity of the bitcells to single event upsets.     

Strength softening and stress relaxation of nanostructured materials

A composite model is proposed to rationalize the phenomena of strength softening with decreasing grain size for nanostructured materials, which is assumed to consist of a grain interior and an amorphous grain-boundary layer. The grain interior deforms elastically under external stresses, while the linear viscoelastic flow is responsible for the plastic deformation of the grain-boundary layer, whose stress “relaxation” follows Maxwell’s equation. The results indicate that the strength of a nanostructured material decreases linearly with decreasing grain size, when the grain size is below a certain threshold. The model is compared with the experimental data from the published studies on nanostructured Cu and Ni. The relevant creep mechanisms for nanostructured materials are also discussed in light of model predictions.     

Effects of rapid heating cyclic heat treatment on microstructures and compression mechanical properties of TiAl-based alloy

By means of rapid heating cyclic heat treatment, the microstructure of a TiAl-based alloy was refined.The colony size and lamellar spacing were measured to be 50 μm and 0.12 μm, respectively. The compression me-chanical properties were determined at room temperature and the best comprehensive mechanical properties can reach σ0.2 of 745.1 MPa, σp of 1672.2 MPa and δ of 19. 40%. The improvement of mechanical properties is caused by the microstructural refinement and the phase interface nucleation contributes a lot to the refinement of microstructure.     

Robust Motion Control for Robotic Assembly Tasks using Variable Structure Control Scheme

The success of robot assembly tasks depends heavily on its ability to handle the interactions which take place between the parts being assembled. In this paper, a robust motion-control method is presented for robot manipulators performing assembly tasks in the presence of dynamic constraints from the environment. Using variable structure model reaching control concept, the control objectives is first formulated as a performance model in the task space. A dynamic compensator is then introduced to form the switching function such that the sliding-mode matches the desired model. A simple variable structure control law is suggested to force the system to reach and stay on the sliding mode so that the specified model is achieved.The proposed method is applied to control the prismatic joint of a selective compliance assembly robot-arm type robot for the insertion of printed circuit board into an edge connector socket. Various amounts of interaction forces are generated during the operation. Experimental and simulation results demonstrated the performance of the variable structure model reaching control approach. In comparison, it is shown that the popular position controllers such as proportional plus derivative control and proportional plus derivative with model-based feedforward control are not suitable for achieving good trajectory tracking accuracy in assembly tasks which experience potential interaction force.