Conical beam control of quadrifilar helical antennas

The conical beam control of quadrifilar helical antennas with a fixed helical arm length is investigated. By adjusting a portion of the antenna height to vary the pitch angle, the elevation angle of the beam direction can be controlled with an almost constant gain. It is found that the elevation angle of the beam direction varies in proportion to the pitch angle     

A novel polymerization process using rotating disk atomizer

Macroporous highly crosslinked styrene(St)-divinylbenzene(DVB) copolymers were prepared by solution and suspension polymerization techniques. The obtained materials allowed the grafting of poly(N-vinyl-tert-butylcarbamate) (PVCa) either by addition of VCa macroradicals to the solid bound double bonds or by termination involving the reaction of VCa macroradicals with radicals present on the carrier. Poly(vinylamine) (PVAm) grafted on St-DVB carriers was obtained after the hydrolysis of grafted PVCa with HCl and the subsequent removal of the aminebonded HCl by means of NaOH. Heterogeneous bifunctional catalysts were obtained by attachment of cobalt(II) 4,4′,4″,4?-tetracarboxyphthalocyanine (CoPc(COOH)₄) to the grafted PVAm. The prepared catalysts were applied to the autoxidation of thiols to disulfides, both in predominantly apolar media and in aqueous media. It was demonstrated, that important prerequisites for the applicability of macroporous St-DVB copolymers as carriers for the PVAm-CoPc(COOH)₄ catalyst include a high surface area, a sufficiently large average pore diameter and accessibility of the pendent double bonds.     

A concept of combined micro and macro fracture mechanics to brittle fracture

Real materials inevitably contain both stress concentrators as cracks or notches and as dislocations, that is both macroscopic and microscopic one. From this viewpoint, a concept of combined micro and macro fracture mechanics is proposed for low-stress brittle fracture of steels.     

Microangioarchitecture of rat parietal cortex with special reference to vascular "sphincters". Scanning electron microscopic and dark field microscopic study

Microangioarchitecture of the rat parietal cortex was studied by means of scanning electron microscopy and dark field microscopy. The richest supply of blood vessels in the parietal cortex was found in layer III + IV and layer V, where 2 isolated plexuses of microvessels were prominent. The appearance of the plexuses was quite different between motor and sensory areas. In the motor area the capillary plexuses were narrow and compact, while in sensory area the plexuses were wide and diffuse. Characteristic ring formations, called ring-shaped-compressions in the present study, were frequently observed at branching sites of arterioles. The ring-shaped-compression probably corresponds to the precapillary sphincter. A similar structure was also seen in capillaries and venules and, therefore, it is likely that not only arterioles, but also capillaries and even venules, can actively change diameter to control cerebral blood flow.     

Rapid and economical indicator for evaluating arsenic removal with minimum aluminum residual during coagulation process

Detection of various types of contaminants in water treatment plant by sophisticated analytical methods such as inductively coupled plasma/mass spectrometry and gas chromatography/mass spectrometry requires hours to days to provide the results. Because naturally occurring ultraviolet (UV) active compounds are commonly present in almost all source waters and can be rapidly monitored by UV absorbance at 260 nm (E260), the extent of correlation between the removal efficiency of E260 and the removal efficiency of As(V) with minimum soluble residual Al by coagulation process was investigated. Percentage removals for E260 were well correlated to those of As(V). When sufficient alum or polyaluminum chloride (PACl) was added for 60-65% removal of E260, 90-95% removal of As(V) was achieved with minimum soluble residual Al regardless of the initial level of turbidity, E260, and As(V). As E260 analysis is precisely available even by an unskilled plant operator in a few minutes, E260 removal efficiency appears to be the promising economical indicator for monitoring the effectiveness of the coagulation process for the removal of contaminants with minimum residual Al.     

A 56-nm CMOS 99-mm2 8-Gb Multi-Level NAND Flash Memory With 10-MB/s Program Throughput

A single 3.3-V only, 8-Gb NAND flash memory with the smallest chip to date, 98.8 mm², has been successfully developed. This is the world's first integrated semiconductor chip fabricated with 56-nm CMOS technologies. The effective cell size including the select transistors is 0.0075 mum² per bit, which is the smallest ever reported. To decrease the chip size, a very efficient floor plan with one-sided row decoder, one-sided page buffer, and one-sided pad is introduced. As a result, an excellent 70% cell area efficiency is realized. The program throughput is drastically improved to twice as large as previously reported and comparable to binary memories. The best ever 10-MB/s programming is realized by increasing the page size from 4kB to 8kB. In addition, noise cancellation circuits and the dual VDD-line scheme realize both a small die size and a fast programming. An external page copy achieves a fast 93-ms block copy, efficiently using a 1-MB block size     

Resonance characteristics and identification of modes of electromagnetic waves excited by partial discharges in GIS

Electromagnetic waves are used for detection of partial discharges (PD) in GIS (gas‐insulated substations). A very wide frequency band up to 1.5 GHz is utilized for detection. There are three categories of electromagnetic wave which can be excited and propagate in coaxial cylindrical structures like GIS, namely, TEM, TE, and TM modes. The characterization and identification of each mode is indispensable to understanding the partial discharge phenomena in GIS. In this paper, peaks in the frequency spectrum excited by PD are identified in each mode and the resonant characteristics of each mode are studied. The following are the major results: (1) The resonance peaks appear at the frequencies defined by the spacer distance. (2) The intensity of each mode depends on the position of discharge source along the radial direction. The lower‐order modes including TEM are excited when a discharge source is located near the center conductor. On the other hand, higher‐order modes are excited when the discharge source is at the enclosure surface. (3) The experimental profile of each mode excited by PD along the radial direction approximately agrees with the general theory of electromagnetic wave propagation in coaxial cylindrical cavity. © 2000 Scripta Technica, Electr Eng Jpn, 131(2): 1–11, 2000     

Low chirp observed in directly modulated quantum dot lasers

We have examined the dynamic properties of high-aspect-ratio InAs-quantum-dot (QD) lasers at room temperature. A novel characteristic of low chirp in the lasing wavelength under 1-GHz current modulation was found in the quantum dot lasers. This is more than one order of magnitude less than the typical chirp (0.2-nm) found in a conventional quantum well laser that we used as a reference. Low chirp was obtained not only in the ground state lasing but in the second level lasing of quantum dots as well.