A new etchant system,K2Cr2O7-H2SO4-HCl,for GaAs and InP

A new K₂Cr₂O₇-H₂SO₄-HCl system has been developed that is particularly suitable for use in etching solutions of GaAs and InP. This system provides high quality etched surfaces without any undesirable roughness or etch pits. It has been found that the etching rate can be controlled by changing the etchant component proportions. This is especially the case with HCl. This leads to no change of surface quality. Vertical walls, and mesa-shaped structures have been formed on etching profiles of (001) GaAs by stripes parallel to the [110], and [¯110] directions, respectively. The mesa-shaped profiles have been formed for (001) InP in both the [110] and [¯110] directions. The solution does not erode photoresist masks and is thereby attractive for a variety of device applications.     

Micromachining of electroformed nickel mold using thick photoresist microstructure for imprint technology

In order to fabricate polymer-based microstructures with feature sizes on the order of micrometers, we have been developing a microimprint technology with a fine nickel (Ni) mold instead of a conventional photolithography technique. The Ni mold was successfully fabricated by electroforming using a positive thick photoresist microstructure patterned on a silicon substrate as a replication master. The photoresist microstructure with excellent edge quality can be obtained under irradiation with single wavelength (g line) selected from a high-pressure mercury lamp. In addition, its sidewall angle in the range of 65° to 84° can be controlled precisely by varying the distance between a photomask and a photoresist surface. On the structured photoresist master, Ni was electroplated up to a thickness of about 110 μm, and then removed from the master. In this process, two-step electroplating at different current densities was carried out in order to prevent deformation of the photoresist master due to stress generated in a Ni electrodeposit. With the Ni mold, fine patterns with a width of 10 or 30 μm and a depth of 24 μm were almost completely transferred to polymetric materials (PMMA). The geometrical dimensions of the fabricated PMMA microstructures were found to be only about 10% reduction against the Ni mold.     

Robust digital control of a DC–DC buck converter with low frequency samplings

A robust DC?CDC converter which can covers extensive load change and also input voltage changes with one controller is needed. Then the demand to suppress output voltage change becomes still severer. We propose an approximate 2-degree-of-freedom (2DOF) digital controller which realized start-up response and dynamic load response independently. The controller makes a control bandwidth wider, and at the same time makes variations of the output voltage small at sudden changes of a load and an input voltage. In this paper, a new approximate 2DOF digital control system with additional zeros is proposed. Using the additional zeros, the second-order differential transfer characteristics between equivalent disturbances and a output voltage are realized. Therefore, the new controller makes variations of the output voltage smaller and the sudden changes of the load and the input voltage. This controller is actually implement on a DSP and is connected to the DC?CDC converter. Experimental results demonstrate that this type of digital controller can satisfy given severe specifications with low frequency sampling.     

An application of the 2-nitrobenzenesulfenyl method to proteomic profiling of human colorectal carcinoma: A novel approach for biomarker discovery

In the development of novel biomarkers, the proteomic approach is advantageous because using it the cancer-associated proteins can be directly identified. We previously developed a 2-nitrobenzenesulfenyl (NBS) method to improve quantitative proteome analysis. Here, we applied this method to proteomic profiling of colorectal carcinoma (CRC) to identify novel proteins with altered expression in CRC. Each pair of tumor and normal tissue specimens from 12 CRC patients was analyzed, and approximately 5000 NBS-labeled paired peaks were quantified. Peaks with altered signal intensities (>1.5-fold) and occurring frequently in the samples (>70%) were selected, and 128 proteins were identified by MS/MS analyses as differentially expressed proteins in CRC tissues. Many proteins were newly revealed to be CRC related; 30 were reported in earlier studies of CRC. Six proteins that were up-regulated in CRC (ZYX, RAN, RCN1, AHCY, LGALS1, and VIM) were further characterized and validated by Western blot and immunohistochemistry. All six were found to be CRC-localized, either in cancer cells or in stroma cells near the cancer cells. These results indicate that the proteins identified in this study are novel candidates for CRC markers, and that the NBS method is useful in proteome mining to discover novel biomarkers.     

Determining number of clusters and prototype locations via multi-scale clustering

In clustering algorithms, it is usually assumed that the number of clusters is known or given. In the absence of such a priori information, a procedure is needed to find an appropriate number of clusters. This paper presents a clustering algorithm that incorporates a mechanism for finding the appropriate number of clusters as well as the locations of cluster prototypes. This algorithm, called multi-scale clustering, is based on scale-space theory by considering that any prominent data structure ought to survive over many scales. The number of clusters as well as the locations of cluster prototypes are found in an objective manner by defining and using lifetime and drift speed clustering criteria. The outcome of this algorithm does not depend on the initial prototype locations that affect the outcome of many clustering algorithms. As an application of this algorithm, it is used to enhance the Hough transform technique.     

Downscaling MODIS LST in the East African mountains using elevation gradient and land-cover information

Land-surface temperature (LST) is strongly affected by altitude and surface albedo. In mountain regions where steep slopes and heterogeneous land cover are predominant, LST can vary significantly within short distances. Although remote sensing currently provides opportunities for monitoring LST in inaccessible regions, the coarse resolution of some sensors may result in large uncertainties at sub-pixel scales. This study aimed to develop a simple methodology for downscaling 1 km Moderate Resolution Spectroradiometer (MODIS) LST pixels, by accounting for sub-pixel LST variation associated with altitude and land-cover spatial changes. The approach was tested in Mount Kilimanjaro, Tanzania, where changes in altitude and vegetation can take place over short distances. Daytime and night-time MODIS LST estimates were considered separately. A digital elevation model (DEM) and normalized difference vegetation index (NDVI), both at 250 m spatial resolution, were used to assess altitude and land-cover changes, respectively. Simple linear regressions and multivariate regressions were used to quantify the relationship between LST and the independent variables, altitude and NDVI. The results show that, in Kilimanjaro, altitude variation within the area covered by a 1 km MODIS LST pixel can be up to ±300 m. These altitude changes can cause sub-pixel variation of up to ±2.13°C for night-time and ±2.88°C for daytime LST. NDVI variation within 1 km pixels ranged between –0.2 and 0.2. For night-time measurements, altitude explained up to 97% of LST variation, while daytime LST was strongly affected by land cover. Using multivariate regressions, the combination of altitude and NDVI explained up to 94% of daytime LST variation in Kilimanjaro. Finally, the downscaling approach proposed in this study allowed an improved representation of the influence of landscape features on local-scale LST patterns.     

Thermal management of edge‐lit wide color gamut backlight for LCD using red laser diodes and cyan LEDs

The color gamut is one of the critical parameters that dictate the image quality of displays. The liquid crystal displays using white color light‐emitting diodes (LEDs) as the backlight, though having been widely employed recently, are not very satisfactory in terms of their color gamut because of the broad spectrum inherent to white LEDs. This prompted the authors to develop improved liquid crystal displays using an edge‐lit wide color gamut backlight that used red laser diodes and cyan LEDs. Generating laser beams with high color purity, the laser diodes are light sources with a significant effect on expanding the color gamut. However, laser diodes, red ones in particular, have unfavorable thermal characteristics. To cope with this shortcoming, the authors clearly defined the restrictive criteria for laying out two kinds of light source on the edge‐lit backlight and made a prototype 55‐type laser backlight for performance evaluation.     

A self-organizing map with twin units capable of describing a nonlinear input-output relation applied to speech code vector mapping

This paper describes a new type of self-organizing map (SOM) with twin units as opposed to the single unit type conventional SOM proposed by Kohonen. The present self-organizing map with twin units (TW-SOM) can describe a nonlinear input-output relation with high accuracy. It is applied to voice conversion problem from bone conduction voice to air conduction voice (nonlinear code vector mapping), and its superiority over the conventional method using Linde-Buzo-Gray (LBG) algorithm is discussed. The tone quality of the converted voice is examined not only from the quantization distortion viewpoint, but also from the auditory sensation viewpoint through actual listening tests. The enhancement of the tone quality was experimentally confirmed.     

Digital copy milling—autonomous milling process control without an NC program

Conventional NC machine tools do not generally allow the change of cutting conditions such as depth of cut and stepover during machining operations, once they are given machining commands as NC programs. For that reason, the NC programs must be prepared adequately and verified in advance, which requires extensive time and effort. It is therefore necessary to develop functions to generate the cutter path autonomously and control the cutting conditions adaptively during machining to optimize the cutting process, maintain stable cutting, and avoid cutting trouble. This paper proposes a new architecture to realize autonomous control of the cutting process without using NC programs. A technique called digital copy milling is developed to control the NC machine tool in real time. The digital copy milling system can generate tool paths in real time, based on the principle of copy milling. In addition, a new control strategy is developed to control the cutting conditions adaptively. A prototype of an autonomous controller was implemented in a three-axis control machining center. Thereafter, experimental milling tests were carried out to verify the effectiveness of the proposed system. The cutter paths were generated autonomously by the digital copy milling system. Results show that the cutting depth and stepover can be changed during milling tests. Cutting conditions were controlled adaptively.