Improvement in Oxidation Resistance of Stainless Steel by Molten-Salt Electrodeposition of La

Improvement in the oxidation resistance of SUS304 stainless steel was accomplished by electrodeposition of La in a molten salt. The electrolysis of La was conducted using a potentiostatic-polarization method in an equimolar NaCl–KCl melt containing 3.5 mol. LaF ₃ at 1023 K. Observation of the specimen surface after polarization at –1.8 V (vs. Ag/Ag⁺ (0.1)) for 0.18 ks showed that La particles were uniformly dispersed on the surface. The oxidation resistance of the electrodeposited stainless steel was significantly improved as compared with the untreated stainless steel. The scale formed on the untreated stainless steel after oxidation was thick and consisted of Fe₂O₃ and Fe₃O₄, whereas the scale formed on the elecrodeposited stainless steel was extremely thin, and mainly consisted of Cr₂O₃.     

Improvement of output voltage control performance for low-speed operation of matrix converter

The matrix converter (MxC) is an ac-to-ac conversion device that can generate variable frequency and variable voltage output. The nine bidirectional switches of an MxC allow pulse-width modulation (PWM) control of input currents and output voltages. PWM switches need "switch commutations" from one switch to another. During these switch commutations, however, unwanted voltage error occurs like a dead time effect in a voltage source inverter (VSI). When PWM pulse-widths are narrower than the time for completing a commutation sequence, voltage error rapidly increases. In the low-speed range, PWM pulses become narrower and voltage distortions become larger due to incomplete commutations. Moreover, these errors are critical in the low-speed operation because the system is sensitive to the smallest voltage error. In this paper, a new PWM strategy is proposed for improving voltage control performance in the low-speed range. Based on the input and output voltage information, PWM pulse-widths are controlled to avoid incomplete commutation. The feasibility of the proposed method is proved through simulation and experimental results.     

A 146-mm/sup 2/ 8-gb multi-level NAND flash memory with 70-nm CMOS technology

An 8-Gb multi-level NAND Flash memory with 4-level programmed cells has been developed successfully. The cost-effective small chip has been fabricated in 70-nm CMOS technology. To decrease the chip size, a one-sided pad arrangement with compacted core architecture and a block address expansion scheme without block redundancy replacement have been introduced. With these methods, the chip size has been reduced to 146 mm/sup 2/, which is 4.9% smaller than the conventional chip. In terms of performance, the program throughput reaches 6 MB/s at 4-KB page operation, which is significantly faster than previously reported and very competitive with binary Flash memories. This high performance has been achieved by the combination of the multi-level cell (MLC) programming with write caches and with the program voltage compensation technique for neighboring select transistors. The read throughput reaches 60 MB/s using 16I/O configuration.     

Development of a 3-D simulation analysis system for PWR control rod drive mechanism

A 3-D virtual analysis system to analyze the motion of control rod drive mechanism (CRDM) was developed. The analysis system consists of a 3-D model established as per the actual dimensions and interfaces of CRDM parts and a routine to calculate the forces acting on the mechanism, and was verified by mock-up test using the same equipment as the actual product. The analysis system is useful for functional evaluation in maintenance or to factor out root causes in the case of malfunction of CRDM.     

Generalized KYP lemma: unified frequency domain inequalities with design applications

The celebrated Kalman-Yakubovic/spl caron/-Popov (KYP) lemma establishes the equivalence between a frequency domain inequality (FDI) and a linear matrix inequality, and has played one of the most fundamental roles in systems and control theory. This paper first develops a necessary and sufficient condition for an S-procedure to be lossless, and uses the result to generalize the KYP lemma in two aspects-the frequency range and the class of systems-and to unify various existing versions by a single theorem. In particular, our result covers FDIs in finite frequency intervals for both continuous/discrete-time settings as opposed to the standard infinite frequency range. The class of systems for which FDIs are considered is no longer constrained to be proper, and nonproper transfer functions including polynomials can also be treated. We study implications of this generalization, and develop a proper interface between the basic result and various engineering applications. Specifically, it is shown that our result allows us to solve a certain class of system design problems with multiple specifications on the gain/phase properties in several frequency ranges. The method is illustrated by numerical design examples of digital filters and proportional-integral-derivative controllers.     

Bone metastasis from colorectal cancer in autopsy cases

The incidence of bone metastasis from colorectal cancer is reported to be 10.7% in autopsy cases. However, the characteristics of the primary cancers, as well as the patterns of bone metastasis, remain unclear. We analyzed the clinical and autopsy records of 118 patients with primary colorectal cancer treated either surgically or conservatively and eventually autopsied between 1970 and 1987 at Toranomon Hospital in Tokyo. Bone metastasis was detected in 23.7% (28/118). The average age of patients with bone metastasis was lower than that in patients without bone metastasis (P < 0.02). Cancers to the rectum and cecum were accompanied by bone metastasis more frequently than cancers of other portions of the colon. Signet-ring cell carcinoma showed a high incidence of bone metastasis (P = 0.041). Bone metastasis from colorectal cancer was associated with liver or lung metastases (P < 0.0001). These results indicated that bone metastasis from colorectal cancer is not as infrequent as previously described.     

Primary spinal leptomeningeal gliomatosis presenting visual disturbance as the initial symptom: case report

We report a case of diffuse leptomeningeal gliomatosis which spread from the cervical to the sacral spine. A 60-year-old man was admitted with visual disturbance due to papilledema. Magnetic resonance imaging revealed holocord leptomeningeal gliomatosis without a definite intraparenchymal lesion, and the patient's neurological examination was unremarkable except for papilledema. Intracranial hypertension secondary to spinal tumor is well known but unusual, and the mechanism is still unclear. In our case, an elevated protein concentration of cerebrospinal fluid is suggested as the cause of intracranial hypertension.