Field Configurable Self-assembly is a novel programmable force field based heterogeneous integration technology. Herein, we demonstrate application of the method to rapid, parallel assembly of similar and dissimilar sub-200 µm GaAs-based light emitting diodes at silicon chip substrates. We also show that the method is compatible with post-process collective wiring techniques for fully planar hybrid integration of active devices.

This paper describes a practical Japanese natural language Question Answering system adopting effective selection of dynamic passages, Lexico-Semantic Patterns (LSP), and Predictive Answer Indexing. By analyzing the previous TREC QA data, we defined a dynamic passage unit and developed a passage selection method suitable for Question Answering. Using LSP, we identify the answer type of a question and detect answer candidates without any deep linguistic analyses of the texts. To guarantee a short response time, Predictive Answer Indexing is combined into our overall system architecture. As a result of the three engineering techniques, our system showed excellent performance when evaluated by mean reciprocal rank (MRR) in NTCIR-3 QAC-1.

In this paper, we present our investigation of Latent Semantic Indexing (LSI) on the local query regions for solving the computation restrictions of the LSI on the global information space. Through the experiments with different SVD dimensionality on the local query regions, the results show that low-dimensional LSI can achieve much better precision than VSM and similar precision to global LSI. Such small SVD factors indicate that there is an almost linear surface in the local query regions. The largest or the two largest singular vectors have the ability to capture such a linear surface and benefit the particular query. In spite of the fact that Local LSI analysis needs to perform the Singular Value Decomposition (SVD) computation for each query, the surprisingly small requirements of the SVD dimension resolve the computation restrictions of LSI for large scale IR tasks. Moreover, on the condition that several relevant sample documents are available, application of low dimensional LSI for these documents can obtain comparable precision with the Local RF in a different manner.

The case postpositions usually have more than one semantic role in Korean. The adverbial postpositions among various postpositions especially make the development of Korean-based machine translation system difficult, because they have more semantic roles than others. In this paper, we describe a new method for resolving semantic ambiguities of adverbial postpositions using decision tree induction. The lack of training examples in decision tree induction is overcome by clustering words into classes using a kind of greedy algorithm. The cross validation results show that the presented method achieves 76.5% of accuracy on the average, which is 20.3% improvement over the baseline method.

A new technique for optical generation of high-purity millimeter-wave (mm-wave) signals--namely, by synthesizing the outputs from cascadingly phase-locked multiple semiconductor lasers--was developed. Firstly, a high-spectral-purity mm-wave signal was optically generated by heterodyning the outputs from two phase-locked external-cavity semiconductor lasers. The beat signal was detected by a p-i-n photodiode whose output was directly coupled to a coax-waveguide converter followed by a W-band harmonic mixer. By constructing an optical phase-locked loop (OPLL), a high-spectral-purity mm-wave signal with an electrical power of 2.3 µW was successfully generated at 110 GHz with an rms phase fluctuation of 57 mrad. Secondly, the frequency of the mm-wave signal was extended by use of three cascadingly phase-locked semiconductor lasers. This technique uses a semiconductor optical amplifier (SOA) to generate four-wave-mixing (FWM) signals as well as to amplify the input signals. When the three lasers were appropriately tuned, two pairs of FWM signals were nearly degenerated. By phase-locking the offset frequency in one of the nearly degenerated pairs, the frequency separations among the three lasers were kept at a ratio of 1:2. Thus, we successfully generated high-purity millimeter-wave optical-beat signals at frequencies at 330.566 GHz with an rms phase fluctuation of 0.38 rad. A detailed analysis of the phase fluctuations was carried out on the basis of measured power spectral densities. The possibility of extending the mm-wave frequency up to 1 THz by using four cascadingly phase-locked lasers was also discussed.

We report on several photoconductive (PC) geometries for the generation of both guided-wave and free-space terahertz (THz) waveforms. It is found that guided-wave THz electrical waveforms can be produced through both PC self-switching and frozen wave generation--eliminating the need for an ultrashort carrier lifetime in the semiconductor substrate. The concept of PC switching is also applied to the generation of free-space THz waveforms, and various ZnSe detectors are investigated as potential electro-optic THz sensors.

Wavelength conversion using the cross-gain modulation (XGM) of amplified spontaneous emission (ASE) in a traveling-wave type semiconductor optical amplifier (TW-SOA) is theoretically studied. Taking into account the spatial and temporal variations of carrier density along the SOA length, output signal and converted ASE waveforms are analyzed. We also reveal the dependency of the signal and converted ASE waveforms on input signal power and repetition frequency, and confirm that numerical analyses well agree with the experimental results. Finally we qualitatively clarify the way to improve frequency response by simulating eye-diagrams for long SOAs and assist light pumping for the first time.

We propose a novel method of precisely measuring the polarization dependence of single pass gain (PDG) in a semiconductor optical amplifier integrated with spot-size convertors (SS-SOA). By averaging the signal gain of a SS-SOA over a wide wavelength range using the amplified spontaneous emission (ASE) of an erbium doped fiber (EDF), the PDG can be accurately estimated. This is because the influence of gain ripples on the measurement results are drastically reduced. We successfully evaluated the PDG of an angled-facet SS-SOA, even before the process of anti-reflection coating, within a small error of 0.5dB. The EDF-ASE technique is useful in sampling tests and selecting angled-facet SS-SOA chips from wafers. The polarization dependence of the coupling efficiency (PDCE) between a SS-SOA and optical fiber is also evaluated by measuring the photo-current of the active layer for TE and TM input signals. It is possible, therefore, to specify the polarization characteristics of the active region and spot-size converter region, which are indispensable parameters for the design of the SS-SOA.

An 80 Gbit/s conventional and carrier-suppressed return-to-zero optical time-division multiplexing signal transmission over a 208 km standard single-mode fiber was experimentally demonstrated. This was achieved by using mid-span optical phase conjugation based on four-wave mixing in semiconductor optical amplifiers. In addition, it was confirmed that the transmitted carrier-suppressed return-to-zero optical signal's carrier phase-relation was held.

This paper presents a maximum likelihood (ML) identification and restoration method for noisy blurred images. The unitary discrete sine transform (DST) is employed to decouple the large order spatial state-space representation of the noisy blurred image into a bank of one-dimensional real state-space scalar subsystems. By assuming that the noises are Gaussian distributed processes, the maximum likelihood estimation technique using the expectation-maximization (EM) algorithm is developed to jointly identify the blurring functions, the image model parameters and the noise variances. In order to improve the computational efficiency, the conventional Kalman smoother is incorporated to give the estimates. The identification process also yields the estimates of transformed image data, from which the original image is restored by the inverse DST. The experimental results show the effectiveness of the proposed method and its superiority over the recently proposed spatial domain DFT-based methods.

This paper describes a highly-portable multilingual question answering system on multiple relational databases. We apply techniques which were verified on open-domain text-based question answering, such as semantic category and pattern-based grammars, into natural language interfaces to relational databases. Lexico-semantic pattern (LSP) and multi-level grammars achieve portability of languages, domains, and DB management systems. The LSP-based linguistic processing does not require deep analysis that sacrifices robustness and flexibility, but can handle delicate natural language questions. To maximize portability, we drive three dependency factors into the following two parts: language-dependent part into front linguistic analysis, and domain-dependent and database-dependent parts into backend SQL query generation. We also support session-based dialog by preserving SQL queries created from previous user's question, and then re-generating new SQL query for the successive questions. Experiments with 779 queries generate only constraint-missing errors, which can be easily corrected by adding new terms, of 2.25% for English and 5.67% for Korean.

In this paper, we consider the problem of multicasting a message in k-ary n-cubes under the store-and-forward model. The objective of the problem is to minimize the size of the resultant multicast tree by keeping the distance to each destination over the tree the same as the distance in the original graph. In the following, we first propose an algorithm that grows a multicast tree in a greedy manner, in the sense that for each intermediate vertex of the tree, the outgoing edges of the vertex are selected in a non-increasing order of the number of destinations that can use the edge in a shortest path to the destination. We then evaluate the goodness of the algorithm in terms of the worst case ratio of the size of the generated tree to the size of an optimal tree. It is proved that for any k 5 and n 6, the performnance ratio of the greedy algorithm is c kn - o(n) for some constant 1/12 c 1/2.

We introduce a clock schedule algorithm to obtain a clock schedule that achieves a shorter clock period and that can be realized by a light clock tree. A shorter clock period can be achieved by controlling the clock input timing of each register, but the required wire length and power consumption of a clock tree tends to be large if clock input timings are determined without considering the locations of registers. To overcome the drawback, our algorithm constructs a cluster that consists of registers with the same clock input timing located in a close area. The registers in each cluster are driven by a buffer and a shorter wire length can be achieved. In our algorithm, first registers are partitioned into clusters by their locations, and clusters are modified to improve the clock period while maintaining the radius of each cluster small. In our experiments, the clock period achieved in average is about 13% shorter than that achieved by a zero-skew clock tree, and about 4% longer than the theoretical minimum. The wire length and power consumption of a clock tree according to an obtained clock schedule is comparable to these of a zero skew tree.

A circuit in which the clock is assumed to be distributed periodically to each individual register though not necessarily to all registers simultaneously, called a semi-synchronous circuit, is expected to achieve higher frequency or a smaller clock tree compared with an ordinary synchronous circuit, called a complete-synchronous circuit. In this paper, we propose a circuit design method that realizes a semi-synchronous circuit with higher frequency by modifying the clock tree of a complete-synchronous circuit. We confirm that the proposed method is easy to incorporate with current practical design environment by designing a four stage pipelined processor compatible with MIPS operation code. The obtained processor circuit is the first semi-synchronous circuit designed systematically with theoretical background.

This paper presents a detailed simulation method to estimate Doppler power spectrum and mean blood velocity using real CW Doppler transducers with twin-crystal arrangement. The method is based on dividing the sample volume into small cells and using the statistics of the Doppler power spectrum with the same Doppler shift frequency, which predicts the mean blood velocity. The acoustic fields of semicircular transducers across blood vessels were calculated and the effects of acoustical and physiological factors on Doppler power spectrum and mean blood velocity were analyzed. Results show that nonuniformity of the acoustic field of the ultrasonic beam in the blood vessel and blood velocity profiles significantly affect Doppler power spectrum and mean blood velocity. However, Doppler angle, vessel depth, and sample volume length are not sensitive functions. Comparisons between simulation and experimental results illustrated a good agreement for parabolic flow profile. These results will contribute to a better understanding of Doppler power spectrum and mean blood velocity in medical ultrasound diagnostics.

A novel self-alignment process using the surface tension of the liquid resin for assembly of electronic or optoelectronic devices in 3-D space has been proposed. The vertical alignment can be controlled by using of metal sphere, reducing the necessary precise process control such as solder volumes and external forces, and allowing large tolerances in liquid volume and misalignment. Lateral alignment could be also achieved by making the liquid resin constrained on the 3-dimensional pads on chip and substrate. This study focused on the principle of self-alignment and final alignment accuracy. In addition, the possibility of self-alignment process was verified by analytic numerical method and scaled-up experiment. An average alignment accuracy of less than 0.25 µm has been obtained. It is thought that this process is effective for assembly simply at low process temperature, low cost and without flux in future assembly techniques.

Semistructured data comprises irregular structure and has no a-priori database schema, therefore we encounter several problems such as inefficient data retrieval and wasteful data storage. To cope with such problems, some schema extraction algorithms over semistructured data have been proposed, in which data is modeled as an unordered tree. However, the order of elements is indispensable for document data, therefore we consider extracting an optimal database schema over an ordered tree. We consider an optimization problem to extract a smallest database schema such that the density of each class is no less than a given threshold, where the density of a class represents a similarity between the type of the class and those of the objects in the class. We first prove that the corresponding decision problem is strongly NP-complete, and show that another version of the problem is strongly NP-hard and belongs to Δ2 P. Then we show that for any r < 3/2, there is no polynomial-time r-approximation algorithm that solves the optimization problem unless P = NP. Finally, we propose a kind of class called bounded class that can be constructed efficiently, then show a polynomial-time algorithm for constructing a database schema by using bounded classes.

This paper discusses a new type of semi-supervised document clustering that uses partial supervision to partition a large set of documents. Most clustering methods organizes documents into groups based only on similarity measures. In this paper, we attempt to isolate more semantically coherent clusters by employing the domain-specific knowledge provided by a document analyst. By using external human knowledge to guide the clustering mechanism with some flexibility when creating the clusters, clustering efficiency can be considerably enhanced. Experimental results show that the use of only a little external knowledge can considerably enhance the quality of clustering results that satisfy users' constraint.

A uniform raised-salicide technology has been investigated using both uniform selective-epitaxial-growth (SEG) silicon and salicide films, to reduce a junction leakage current of shallow source/drain (S/D) regions for high-performance CMOS devices. The uniform SEG-Si film without pits is formed by using a wet process, which is a carbon-free oxide removal only using a dilute hydrofluoric acid (DHF) dipping, prior to the Si-SEG process. After a titanium-salicide formation using a conventional two-step salicide process, this uniform SEG-Si film achieves good S/D junction characteristics. The uniform titanium-salicide film without bowing into a silicon is formed by a smaller Ti/SEG-Si thickness ratio, which results in a low sheet resistance of 5 Ω/sq. without a narrow-line effect. Furthermore, the drive current is maximized by this raised-salicide film using a Ti/SEG-Si thickness ratio of 1.0.

Gallager has defined an ensemble of regular low density parity check (LDPC) codes for deriving the ensemble performance of regular LDPC codes. The ensemble is called the Gallager ensemble. In this paper, we define a new ensemble of LDPC codes, called extended Gallager ensemble, which is a natural extension of the Gallager ensemble. It is shown that an extended Gallager ensemble has potential to achieve larger typical minimum distance ratio than that of the original Gallager ensemble. In particular, the extended Gallager ensembles based on the Hamming and extended Hamming codes have typical minimum distance ratio which is very close to the asymptotic Gilbert-Varshamov bound. Furthermore, decoding performance of an instance of an extended Gallager ensemble, called an extended LDPC code, has been examined by simulation. The results show good block error performance of extended LDPC codes.