Retardation of Crystallization of Diacylglycerol Oils Using Polyglycerol Fatty Acid Esters

Liquid oil containing high concentrations of diacylglycerols (DAG > 80 %, hereafter referred to as DAG-rich oil) is generally more likely to cause precipitation at chilled temperatures (clouding phenomena) than triacylglycerol-based oil. The clouding phenomena that occur during long-term storage of DAG-rich oil are unwanted in consumer products and therefore, must be prevented. In the present study, we attempted to retard precipitation by adding food emulsifiers, polyglycerol fatty acid esters (PGFE) containing different fatty acid moieties. DSC, polarized optical microscopy, and X-ray diffraction studies revealed that the addition of 0.2 % PGFE containing palmitic and oleic acid moieties very effectively retarded precipitation in the DAG-rich oil. To confirm these observations, we prepared a model DAG oil to mimic DAG-rich oil and examined the retardation behavior of high-melting DAG fractions using PGFE. The results are discussed in terms of the effects of PGFE additives on the pre-nucleation processes of high-melting fractions in DAG-rich oil.     

A 0.2-μm self-aligned selective-epitaxial-growth SiGe HBTfeaturing 107-GHz fmax and 6.7-ps ECL

A 0.2-μm self-aligned selective-epitaxial-growth (SEG) SiGe heterojunction bipolar transistor (HBT), with shallow-trench and dual-deep-trench isolations and Ti-salicide electrodes, has been developed. The 0.6-μm-wide Si-cap/SiGe-base multilayer was selectively grown by UHV/CVD. The process, except the SEG, is almost completely compatible with well-established bipolar-CMOS technology and the SiGe HBTs were fabricated on a 200-mm wafer line. The SiGe HBTs have demonstrated a peak cutoff frequency of 90 GHz, a peak maximum oscillation frequency of 107 GHz, and an ECL gate delay time of 6.7 ps. Four-level interconnects, including MIM capacitors and high-Q inductors, were formed by chemical mechanical polishing     

Performance enhancement of strained-Si MOSFETs fabricated on a chemical-mechanical-polished SiGe substrate

Chemical-mechanical-polishing (CMP) was used to smooth the surface of a SiGe substrate, on which strained-Si n- and p-MOSFETs were fabricated. By applying CMP after growing the SiGe buffer layer, the surface roughness was considerably reduced, namely, to 0.4 nm (rms). A strained-Si layer was then successfully grown on the CMP-treated SiGe substrate. The fabricated strained-Si MOSFETs showed good turn-off characteristics, (i.e., equivalent to those of Si control devices). Moreover, capacitance-voltage (CV) measurements revealed that the quality of the gate oxide of the strained-Si devices was the same as that of the Si control devices. Flat-band and threshold voltages of the strained-Si devices were different from those of the Si control devices mainly due to band discontinuity. Electron and hole mobilities of strained-Si MOSFETs under a vertical field up to 1.5 MV/cm increased by 120% and 42%, respectively, compared to the universal mobility. Furthermore, current drive of the n- and p-MOSFETs (L/sub eff//spl ges/0.3 /spl mu/m) was increased roughly by 70% and 50%, respectively. These improvements in characteristics indicate that CMP of the SiGe substrate is a critical technique for developing high-performance strained-Si CMOS.     

Structural characteristics of the pedicle and its role in screw stability

STUDY DESIGN: Cross-sectional regional bone mineral density of the pedicle was measured by peripheral quantitative computed tomography. Biomechanical tests were performed to clarify the role of the pedicle in screw stability. OBJECTIVES: To identify the structural characteristics of the pedicle that supports pedicle screw stability and the differences in these characteristics between normal and osteoporotic vertebrae. SUMMARY OF BACKGROUND DATA: The pedicle screw is an essential component of many systems used to align the spine. The contribution of the pedicle to screw stability, however, has not been fully investigated. METHODS: Trabecular, subcortical, and cortical bone mineral density and the area of the pedicle were measured by peripheral quantitative computed tomography. Bone mineral density also was recalculated in four circumferential layers. These parameters were compared between normal and osteoporotic individuals. The relative contribution of the pedicle to screw stability was evaluated by caudocephalad and pull-out loading in a vertebra with or without its body. RESULTS: Inner trabecular, middle subcortical, and outer cortical bone mineral density and cortical bone area in the pedicle were significantly lower in osteoporotic vertebrae than those in normal vertebrae. In the pedicle, bone mineral density increased close to the outer layer. Bone mineral density not as thick even in the outer layer in osteoporotic subjects. Approximately 80% of the caudocephalad stiffness and 60% of the pullout strength of the pedicle screw depended on the pedicle rather than on the vertebral body. CONCLUSION: Screw stability depends on the structural characteristics of the pedicle. The pedicle was denser in the subcortical bone, in which the threads of the screw engage, than in trabecular bone. In osteoporosis, bone mineral density was not as dense even in the outer layer, and the cortex was thinner than normal. A larger screw would not enhance screw stability and may break the thin cortex in osteoporotic vertebrae.     

Effect of the temperature dependence of fluid properties on the migration of an interface in double-diffusive natural convection

Experimental observation has shown that a slightly tilted sharp interface between two convection layers in double-diffusive natural convection migrates perpetually upward gradually with time. This movement of an interface cannot be explained by a simple mathematical model of constant physical properties. The present paper studies the numerical analyses of two-layer convection with the temperature dependence of the properties of the fluid. The perpetual upward migration of an interface was found to be promoted mainly by the temperature dependence of the volumetric coefficient of thermal expansion and also by that of the kinematic viscosity. However, the diffusion coefficient was independent of the migration. The upward migration of an interface appears to be caused by the difference between the intensity of etching due to the flow along the hot wall in the lower layer and that along the cold wall in the upper layer.     

A 0.2-μm 180-GHz-fmax 6.7-ps-ECL SOI/HRS self-alignedSEG SiGe HBT/CMOS technology for microwave and high-speed digitalapplications

A technology for combining 0.2-μm self-aligned selective-epitaxial-growth (SEG) SiGe heterojunction bipolar transistors (HBTs) with CMOS transistors and high-quality passive elements has been developed for use in microwave wireless and optical communication systems. The technology has been applied to fabricate devices on a 200-mm SOI wafer based on a high-resistivity substrate (SOI/HRS). The fabrication process is almost completely compatible with the existing 0.2-μm bipolar-CMOS process because of the essential similarity of the two processes. SiGe HBTs with shallow-trench isolations (STIs) and deep-trench isolations (DTIs) and Ti-salicide electrodes exhibited high-frequency and high-speed capabilities with an f_max of 180 GHz and an ECL-gate delay of 6.7 ps, along with good controllability and reliability and high yield. A high-breakdown-voltage HBT that could produce large output swings for the interface circuit was successfully added. CMOS devices (with gate lengths of 0.25 μm for nMOS and 0.3 μm for pMOS) exhibited excellent subthreshold slopes. Poly-Si resistors with a quasi-layer-by-layer structure had a low temperature coefficient. Varactors were constructed from the collector-base junctions of the SiGe HBTs. MIM capacitors were formed between the first and second metal layers by using plasma SiO₂ as an insulator. High-Q octagonal spiral inductors were fabricated by using a 3-μm thick fourth metal layer     

Applying data mining to a field quality watchdog task

This article describes a watchdog program that discovers “meaningful” repair cases from a field service database. “Meaningful” cases are those judged worth probing further to prevent an epidemic of quality problems. Our system has employed the apriori algorithm, a data mining technique that efficiently performs the basket analysis. Our system proves that this data mining technique is not only useful in knowledge discovery but is also capable of performing the database watchdog task. The apriori algorithm automatically generates frequent itemsets from a large set of records. A frequent itemset is an arbitrary combination of values that appear more often than a threshold “minimum support.” The algorithm often generates too many itemsets for quality engineers to review carefully in their daily work. Many itemsets do not provide sufficient information to investigate further. Hence, in order not to generate these valueless itemsets, the apriori algorithm is modified in two ways. One way is “basket analysis on objective and explanatory attributes” and the other is “itemset reduction.” The advantage of our method is demonstrated with some experimental results. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 18–25, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10034     

Crystal face dependent chemical effects in surface-enhanced Raman scattering at atomically defined gold facets

Among electromagnetic and chemical (CM) contributions to surface-enhanced Raman scattering (SERS), the former is becoming controllable according to the recent progress in nanofabrication of plasmonic metal structures. However, it is still difficult to control the latter effect. Here, the degree of each contribution to SERS signals is examined on well-defined single crystalline facets of gold by using optical field localization within sphere-plane type plasmonic cavities. Crystal face dependent SERS studies of aminobenzenthiol adsorbates clearly show the distinction between CM enhancements on different surfaces, suggesting that the CM-activity of "SERS-hotspots" is closely related to interfacial dipoles formed at metal-molecular junctions.     

Contribution of Ti addition to characteristics of extruded Cu40Zn brass alloy prepared by powder metallurgy

The aim of this paper was to investigate the properties of Cu40ZnTi for the purpose of developing a new high-strength, lead-free brass by powder metallurgy. The effect of Ti addition on precipitation hardening behavior of Cu40Zn (denoted as BS40) brass was studied with respect to mechanical properties and microstructures. BS40 and Cu40Zn − 1.0 wt.%Ti (denoted as BS40-A) brass powders were prepared by water atomization process, and β phase was retained in the raw powders predominately. The BS40 powder and Ti powder were elementally mixed to prepare Cu40Zn + 0.5 wt.%Ti (denoted as BS40-B) and Cu40Zn + 1.0 wt.%Ti (denoted as BS40-C) premixed powders. The alloy powders and premixed powders were solidified at 1053 K for 600 s by spark plasma sintering (SPS) and extruded subsequently. It was observed that Cu₂ZnTi intermetallic compound (IMC) and CuZnTi metastable phase resulted from the reaction between Ti and CuZn showed distinct grain refinement effect on extruded Cu40Zn brass. Thus, the excellent strengthening effect processes by precipitation hardening and deform working was obtained, which responding to an yield strength of 345 MPa, and a ultimate tensile strength of 597 MPa, showed 65.9% and 30.4% higher than that of extruded Cu40Zn brass, respectively.     

Synthesis and electrochemical characterization of Pt catalyst supported on Sn0.96Sb0.04O2−δ with a network structure

We synthesized a Pt catalyst supported on Sn_0.96Sb_0.04O_2−δ with a random network structure for the cathode of the polymer electrolyte fuel cell (PEFC). The Sn_0.96Sb_0.04O_2−δ support, synthesized by the flame combustion method, was in the form of nanometer-sized particles with a partially agglomerated structure similar to that of carbon black (CB) and with a high surface area, 125 m² g⁻¹. The structure was considered to be beneficial in reducing the contact resistance between the Sn_0.96Sb_0.04O_2−δ support particles and in dispersing the nanometer-size Pt particles. We applied the nanocapsule method to synthesize the Sn_0.96Sb_0.04O_2−δ-supported Pt catalyst (Pt/Sn_0.96Sb_0.04O_2−δ). The electrochemically active surface area (ECA) of Pt reached a maximum of 60.2 m² g_(Pt)⁻¹, and the high values were maintained during the potential step cycling test (0.9–1.3 V) simulating the start/stop cycling of PEFCs. The oxygen reduction reaction activity of the Pt/Sn_0.96Sb_0.04O_2−δ catalyst exceeded that of Pt supported on carbon black (Pt/CB). We conclude that the random network structured Sn_0.96Sb_0.04O_2−δ might be a good candidate support material for the cathode of PEFCs.