Polymerization of propylene over metal oxides-supported TiCl3 catalysts

Summary Several metal oxides-supported TiCl₃ catalysts were prepared and propylene polymerization was conducted over them without cocatalysts. It was found that isotactic polymerization of propylene took place effectively over them.     

On the possible patterns of inputs for block sorting in the Burrows-Wheeler transformation

Block sorting in the Burrows-Wheeler transformation is to sort all of the n circular shifts of a string of length n lexicographically. We introduce a notion called the width of a sequence of n strings of length n and show that the values of widths are very different between the two types of sequences of strings; (1) a sequence of n randomly generated strings of length n, and (2) the sequence of n circular shifts of a randomly generated string of length n.     

Output intersampling approach to direct closed-loop identification

A new direct closed-loop identification method, which uses the output intersampling technique, is proposed in this note. By using the intersampled plant input-output data, the proposed method removes the traditional restrictive identifiability condition, and does not require an external persistently exciting (PE) test signal     

Correction and evaluation of the effect due to parasitic motion on primary accelerometer calibration

Primary accelerometer calibration is carried out under the assumption that a vibration exciter gives a rectilinear motion to an accelerometer to be calibrated. However practical vibration given by the vibration exciter includes parasitic motion such as transverse, rocking, and bending motion. Such parasitic motion would give two serious effects on primary calibration results, transverse motion effect and vibration distribution effect. Transverse motion effect is caused by an inner product of the vectors of both transverse motion and transverse sensitivity. On the other hand, the vibration distribution effect is caused by relative motion between a sensing point of accelerometer and a spot sensed by the interferometer. As these effects have close interaction between parasitic motion and measuring instruments, it would be very difficult to evaluate them by measuring independently each component.     

Effects of Sampling Tube Geometry on Soft Clayey Sample Quality Evaluated by Nondestructive Methods

Sample disturbance caused by difference in sampling tube geometry was evaluated by two nondestructive methods: the measurement of the residual effective stress (p_r') by ceramic disc; and the use of the bender element to ascertain the shear wave velocity (V_s), and thus the maximum shear modulus (G_BE). Samples were measured under atmosphere, i.e., not under confined stress conditions. The soil samples were obtained from two sources: reconstituted Kasaoka clay prepared in the laboratory, and at the test site at Takuhoku, Hokkaido, Japan. Samplers with different geometrical designs, referring to the Japanese standard stationary piston sampler, were used for the model ground and field sampling. The geometrical effects of the sampling tube, for example, the thickness of the tube wall, the edge angle, and the existence of a piston were carefully examined. The quality of the samples taken with different samplers was evaluated by p_r' and G_BE, values which were normalized by the in situ vertical effective stress (σ'_vo) and G_f measured by the seismic cone test in the field. It was found from these studies that p_r'/σ'_vo and G_BE/G_f vary considerably due to the geometry of the sampler, with the edge angle of sampling tubes being the most important feature in obtaining high quality samples. The wall thickness, and thus, the area ratio of the sampler is not critical to the sample quality if the edge angle is sharp enough. The existence of the piston does not significantly influence the sample quality in field samples. Furthermore, the correlation between G_BE and p_r' was also investigated, and it was found that the two parameters are strongly dependent.     

GPC Profile Change of Potato Starch with Extrusion Processing

Native potato starch (moisture content 15%) was treated by twin screw extruder under four operating conditions with varying barrel temperatures (110°C–230°C). These modified starch samples were compared to native and drum-dried starch. Starch sample solution for gel chromatography was prepared by the three methods (acidic, alkaline, and neutral methods). They were subjected to gel chromatography on Toyopearl HW-75, and some difference was found among the three gel chromatographic patterns obtained from the same starch solution. This discrepancy among GPC patterns suggests formation of some types of anhydro-bonds between chains of amylopectin and or amylose in the extrusion process. Elevating barrel temperature increases degree of depolymerization. The size of fragments formed with the treatment is bigger than that of oligosaccharides but smaller than that of amylose.     

Explanation of impact load curve in ball impact test in relation to thermal aging

Solder joints are required to have high impact strength for use in portable electronic products. To make solder joints with high impact strength, qualitative evaluation methods of impact strength are required. Ball impact tests have been widely adopted in evaluating the impact strength of solder joints because of their easy implementation. Impact load curves obtained from ball impact tests are used as an evaluation indicator of impact strength of solder joint. However, a relation between fracture behavior and impact load curve has not yet been clarified, and an explanation of the impact load curve has not yet been provided in detail. In addition to this, detailed study about the relation between IMC layer thickness and impact strength has not been performed, although the IMC layer thickness formed at the interface would significantly affect the impact strength of the solder joint. This study aimed to explain the impact load curve in the ball impact test and to reveal the effect of the IMC layer thickness on the impact strength of the solder joint. Sn–3.0Ag–0.5Cu solder was reflowed on an electroless Ni–P plated Cu substrate (Ni–P), and a ball impact test was then carried out to evaluate the impact strength. This study found that the ball impact test is effective to evaluate the interfacial strength of solder joints. In the impact load curve, it is estimated that the solder bump keeps deforming until the interfacial crack initiates (maximum load), and the interfacial crack initiates after the maximum load and propagates along the interface between the solder and Ni–P. The suitable evaluation of impact strength became possible by measuring the correspondence relation between the deformation distance of the solder bump after fracture and the energy until maximum load and the relation between the area fraction of the residual solder on the fractured pad and the energy after maximum load. And, it is proved that the impact strength decreased with increasing aging time because the growth of the IMC layer remarkably degraded the interfacial strength of the solder joint.     

A design technique for a high-gain, 10-GHz class-bandwidth GaAsMESFET amplifier IC module

A design procedure is proposed for a high-gain and wideband IC module, using stability analysis and a unified design methodology for ICs and packages. A multichip structure is developed using stability analysis and the requirements for stable operation are determined for each IC chip, package, and interface condition between them. Furthermore, to reduce the parasitic influences, several improvements in the interface and package design are clarified, such as wideband matching and LC resonance damping. IC design using effective feedback techniques for enlarging the bandwidth are also presented. The ICs are fabricated using 0.2-μm GaAs MESFET IC technology. To verify the validity of these techniques, an equalizer IC module for 10-Gb/s optical communication systems was fabricated, achieving a gain of 36 dB and a bandwidth of 9 GHz     

A differential photoconductive AND gate with Be-dopedlow-temperature-grown InGaAs-InAlAs MQW MSM-PD's

A novel photoconductive AND gate that overcomes the problems of: 1) the long tail of photoconductive switches and 2) signal leakage via switch capacitance (signal feedthrough) is proposed. We use Be-doped low-temperature (LT)-grown InGaAs-InAlAs MQW metal-semiconductor-metal photodetectors (MSM-PD's) to get a shorter turn-off time and propose a differential AND gate to cancel the signal feedthrough. A comparison between LT-grown MSM-PD's and those fabricated by ion implantation shows that the LT-grown ones are ultrafast with a full width at half maximum of 5.3 ps and are suitable for low-bias operation. It is experimentally confirmed that the differential AND gate completely cancels the signal feedthrough in the picosecond region. The differential AND gate: with the LT MSM-PD's achieves return-to-zero (RZ) 20 Gb/s AND operation