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A Langmuir probe was used to measure electron energy distribution function in an inductively coupled rf Ar discharge.

Research describing the detection of electronegative plasmas by means of a Langmuir probe is presented. In particular the radial model for positive ion collection is developed.

Research was conducted to determine how the test function can be applied in the detection of the negative ion and electron parameters using a proposed theoretical model. Numerical procedures for processing the Langmuir probe properties were also described. Plasma parameters were detected with a spherical probe for various SF6 concentrations. The parameters were in good agreement with the results of negative ion plasmas in previous experiments.

A method that allows easy and inexpensive detection of negative ions is introduced. The method is based upon the electrostatic lens effect of the sheath layer evolving to a positively biased planar probe that focuses the negative charges to distinct regions on the surface. Trajectories of negative ions inside the sheath are obtained after computing the potential and electric field distribution by solving in three dimensions the nonlinear Poisson equation. The negative ions’ flux to square and disk probes is developed in Ar/SF[sub 6] and O[sub 2] plasmas. The method allows negative ion detection with sensitivity higher than that of Langmuir probes. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A global model for electronegative plasma, in which the negative ion distribution is assumed to be a parabolic profile in the axial direction with a flat central region and a similar edge profile in the radial direction in the electronegative region, is applied to study the power and pressure dependences of plasma parameters in low-pressure CF[sub 4] discharges. The electron density increases approximately linearly with the power. The electron temperature also increases with the power due to the decrease in neutral number density with increase in power, resulting in the increase in plasma potential. The density of CF[sup +, sub 3] is a weak function of the power, while the densities of CF[sup +, sub 2], CF[sup +], and F[sup +], which are strongly correlated to the densities of the respective radicals, depend on the power. On the other hand, the decrease in electron temperature with the pressure significantly results in a decrease in the degree of dissociation. The electron density also decreases gradually with the pressure except for the case of pressure lower than 5 mTorr. The densities of CF[sup +, sub 2], CF[sup +], and F[sup +] decrease gradually with the pressure at pressures higher than 5 mTorr, while the density of CF[sup +, sub 3] increases gradually with the pressure. The electron energy probability function (EEPF) is measured with a Langmuir probe in an inductively coupled rf (13.56 MHz) CF[sub 4] discharge over a pressure range from 2 to 30 mTorr, while keeping the power injected into the plasma at about 70 W. The measured EEPFs are approximately Maxwellian at any pressure, although there is a slight deviation from a Maxwellian distribution at pressures higher than 10 mTorr. The results estimated from the measured EEPF are compared to the model and show reasonably good agreement. [ABSTRACT FROM AUTHOR]

The investigation of three-wave interactions among self-excited nonlinear ionization waves in a diffusion-controlled helium positive column showed that two self-excited waves generate the third one by resonance due to nonlinear interaction satisfying the selection rule. There is a mismatch in wave number in three-wave interaction but none in frequency. Strong phase coherence is detected in the nonlinear interaction closely related to the modulational instability.

Research is done on microdischarge (MD) devices which are plasma sources typically operating at 100s Torr to atmospheric pressure with dimensions of 10s--100s micrometre. In conclusion, MD devices having similar magnitudes and spatial distributions of plasma and excited state densities can be obtained to dimensions of, 15 micro meter by keeping pd and current density constant, and having a cathode fall thickness small compared to the characteristic dimension.

Research is done on magnetically enhanced, capacitively couple radio frequency plasma sources, which are finding continued use for etching of materials for microelectronics fabrication. In conclusion, subtle variations in the electrical geometrical layout of the reactor significantly affect the spatial uniformity of ion energy distributions.

Research is done on a method, which allows easy and inexpensive detection of negative ions. In conclusion, the negative ions' flux to square and disk probes, which is developed in Ar/SF6 and O2 plasmas and the method, allows negative ion detection with sensitivity higher than that of Langmuir probes.

Presents a study which the describes a test function for negative ion and electron parameters in plasma. Description of the numerical procedures for the processing of the Langmuir probe characteristics; Type of device the experiments were conducted in.

Investigates the behavior of ionization wave packets in wave-free positive columns of Ne-N[sub2] and helium. Diagram of the experimental apparatus; Discussion on the phenomenological description of wave packet propagation within finite column.

Deals with a study which examined the excitation of nonlinear ionization waves caused by three-wave interaction in helium positive columns. Observation on the bispectrum and bicoherence spectrum; Description of self-excited fluctuations; Characteristics of detected phase coherence in the nonlinear interaction.

Background: One of the barriers for the effective use of computerized health-care related text is the ambiguity of abbreviations. To date, the task of disambiguating abbreviations has been treated as a classification task based on surrounding words. Application of this framework for languages that have no word boundaries requires pre-processing to segment a sentence into separate word sequences. While the segmentation processing is often a source of problem, it is unknown whether word information is really requisite for abbreviation expansion.Objectives: The present study examined and compared abbreviation expansion methods with and without the incorporation of word information as a preliminary study.Methods: We implemented two abbreviation expansion methods: 1) a morpheme-based method that relied on word information and therefore required pre-processing, and 2) a character-based method that relied on simple character information. We compared the expansion accuracies for these two methods using eight medical abbreviations. Experimental data were automatically built as a pseudo-annotated corpus using the Internet.Results: As a result of the experiment, accuracies for the character-based method were from 0.890 to 0.942 while accuracies for the morpheme-based method were from 0.796 to 0.932. The character-based method significantly outperformed the morpheme-based method for three of the eight abbreviations (p < 0.05). For the remaining five abbreviations, no significant differences were found between the two methods.Conclusions: Character information may be a good alternative in terms of simplicity to morphological information for abbreviation expansion in English medical abbreviations appeared in Japanese texts on the Internet. [ABSTRACT FROM AUTHOR]

Objectives: In medical institutions, unauthorized access points and terminals obstruct the stable operation of a large-scale wireless local area network (LAN) system. By establishing a real-time monitoring method to detect such unauthorized wireless devices, we can improve the efficiency of security management.Methods: We detected unauthorized wireless devices by using a centralized wireless LAN system and a location detection system at 370 access points at the University of Tokyo Hospital. By storing the detected radio signal strength and location information in a database, we evaluated the risk level from the detection history. We also evaluated the location detection performance in our hospital ward using Wi-Fi tags.Results: The presence of electric waves outside the hospital and those emitted from portable game machines with wireless communication capability was confirmed from the detection result. The location detection performance showed an error margin of approximately 4 m in detection accuracy and approximately 5% in false detection. Therefore, it was effective to consider the radio signal strength as both an index of likelihood at the detection location and an index for the level of risk.Conclusions: We determined the location of wireless devices with high accuracy by filtering the detection results on the basis of radio signal strength and detection history. Results of this study showed that it would be effective to use the developed location database containing radio signal strength and detection history for security management of wireless LAN systems and more general-purpose location detection applications. [ABSTRACT FROM AUTHOR]

Objective: We have been developing a decision support system that uses electronic clinical data and provides alerts to clinicians. However, the inference rules for such a system are difficult to write in terms of representing domain concepts and temporal reasoning. To address this problem, we have developed an ontology-based mediator of clinical information for the decision support system.Methods: Our approach consists of three steps: 1) development of an ontology-based mediator that represents domain concepts and temporal information; 2) mapping of clinical data to corresponding concepts in the mediator; 3) temporal abstraction that creates high-level, interval-based concepts from time-stamped clinical data. As a result, we can write a concept-based rule expression that is available for use in domain concepts and interval-based temporal information. The proposed approach was applied to a prototype of clinical alert system, and the rules for adverse drug events were executed on data gathered over a 3-month period.Results: The system generated 615 alerts. 346 cases (56%) were considered appropriate and 269 cases (44%) were inappropriate. Of the false alerts, 192 cases were due to data inaccuracy and 77 cases were due to insufficiency of the temporal abstraction.Conclusion: Our approach enabled to represent a concept-based rule expression that was available for the prototype of a clinical alert system. We believe our approach will contribute to narrow the gaps of information model between domain concepts and clinical data repositories. [ABSTRACT FROM AUTHOR]