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The adsorption capacity of fine rubber particle media (FRPM) derived from discarded vehicle tires and the consumer wasted rubber sources was evaluated for hydrogen sulfide treatment. H2S breakthrough tests were performed at various zinc contents, temperatures, and packing quantities. High zinc concentrations increased the adsorption capacity of FRPM significantly. H2S removal by FRPM was optimized at a packing quantity of 75 % of the column volume, and the adsorption capacity increased with reactor temperature within the range of 20–85 °C. The regeneration of ZnCl2 solution was reliable for increasing regeneration capacity of the FRPM-adsorbed H2S. FRPM seems to be an attractive alternative of H2S adsorbents in terms of cost effectiveness compared to traditional materials.

Performance of the laboratory-scale recycled rubber particles (RRP) biofilter was compared to a conventional gravel system and a peat biofilter for treatment of septic tank effluent. During the study, the RRP biofilter provided similar or better performance than other systems in terms of organic removal and hydraulic capacity. After the start-up period, RRP biofilter achieved removal efficiencies for BOD5, total suspended solids (TSS), ammonia nitrogen of 96%, 93%, and 90%, respectively, over the range of hydraulic loading rates of 57-204 L/m2/d. On the other hand, the peat biofilter failed hydraulically and the gravel system showed high TSS concentrations in the effluent. RRP provided high surface area and sufficient time for biological treatment. In addition, RRP was observed to provide ammonia adsorption capacity. The results showed that RRP has the potential to be used as substitutes for natural aggregate such as gravel in septic system drainfields. The RRP biofilter can be used as alternative septic systems for the sites where an existing septic system has failed or site conditions, such as high groundwater table or small lot size, are not suitable for the installation of conventional septic systems.

A commercial rubber waste product, fine rubber particle media (FRPM), was found to adsorb hydrogen sulfide (H2S) at 0.12 mg H2S/g FRPM of adsorption capacity. Since FRPM seems to be an attractive alternative to treat H2S owing to its economic advantages as well as its physicochemical characteristics, several analyses were conducted to investigate fundamental information, surface properties, and breakthrough characteristics of FRPM as adsorbent. The physical properties of FRPM including composition and surface chemistry were investigated to compare its performance with commonly available commercial H2S adsorbents such as activated carbon and assess the possible adsorption mechanism. The specific surface area of FRPM was less than 1% of activated carbon. FRPM does not have enough surface area supporting a pure physical adsorption of H2S because it is particulate in nature with limited porosity. The adsorption of FRPM to remove H2S was complex mechanism and involved a combination of zinc compounds and carbon black.

We investigate the role of contact location information on the perception of local features during contour following in a virtual environment. An absolute identification experiment is conducted under force-alone and force-plus-contact-location conditions to investigate the effect of the contact location information. The results show that the participants identify the local features significantly better in terms of higher information transfer for the force-plus-contact-location condition, while no significant difference was found for measures of the efficacy of contour following between the two conditions. Further data analyses indicate that the improved identification of local features with contact location information is due to the improved identification of small surface features.

The control module controlling points has become high-tech. but the introduction of relevant company`s inspection intervals and methods, and the adoption of the way which is used in relay interlock system became the cause of a failure by excessive and incorrect maintenance. The Human error in failure recovery process can cause vital accidents including train derailment, the points monitoring system could prevent this problem by monitoring points` operation condition in real time. After conducting the changed inspection intervals that applied the results of the criticality of each failure type, MTBF, MTTR, availability, maintainer`s opinion, the work became simplified, and, the failure did not occur for 4 consecutive years in contrast to the previous annual average of 11 failures.

Bu 3 Sn-endded poly(vinyl)s with biological activity were obtained by the radical polymerization of vinyl monomersusing thianthrene cation radical/ n Bu 3 H. Thianthrene cation and stannyl radicals promoted the homopolymerization andcopolymerization of styrene and ethyl vinyl ether having number average molecular weights of 2000-3100. Tributyltinhydride functions as a chain transfer agent. Such polymereization by cationic thianthrene and stannyl radicals could providesome clues for the biological reaction in living animals. Plausible polymerization mechanisms were suggested.Key words: Thianthrene, Cation Radical, Tribuyltin Hydride, Polymerization 1. Introduction Radical chemistry has received great attention due toits main role in various important organic reactions [1] .Nevertheless, little is known for the reactions withunsaturated alkenes and alkynes although cationic rad-icals are known to react with various nucleophiles [1] .The addition of cationic radicals such as R 2 NH

The objective of this paper is to give a general understanding for the development flight test of Korean Utility Helicopter(KUH). This paper contains the contents of detailed flight test plan, the type of flight test, an introduction to main flight test area, and the overview of flight test results. At the beginning, more than 8,500 test points were identified for airworthiness certification to show the compliance for the KUH development requirements. However, the number of flight test points were optimized to 7,800 at the end. To accomplish the test objectives, about 860 flight test sorties had been performed, and more than 1,000 test sorties were consumed for trouble shooting. This paper also describes some major issues faced during development flight test phase.Keywords : Korean Utility Helicopter(한국형 기동헬기), Flight Test Plan(비행시험 계획), Development Flight Test(개발비행시험), Airworthiness Certification(감항인증)

We investigate the accuracy with which the haptic sharpness perception of a virtual edge is matched to that of a real edge and the effect of the virtual surface stiffness on the match. The perceived sharpness of virtual edges was estimated in terms of the point of subjective equality (PSE) when participants matched the sharpness of virtual edges to that of real edges with a radius of 0.5, 2.5, and 12.5 mm over a virtual stiffness range of 0.6 to 3.0 N/mm. The perceived sharpness of a real and a virtual edge of the same radius was significantly different under all but one of the experimental conditions and there was a significant effect of virtual surface stiffness on the accuracy of the match. The results suggest that the latter is presumably due to a constant penetration force employed by the participants that influenced the penetration depth and perceived sharpness of virtual edges at different surface stiffness levels. Our findings provide quantitative relations for appropriately offsetting the radii of virtual edges in order to achieve the desired perceived sharpness of virtual edges.

Tributyltin hydride (), an endocrine disruptor, was slowly polymerized by the group 4 -selectride (Cp`

We numerically investigate a potential fault activation in Tarim Basin, west China, during hydraulic fracturing operations, by considering rigorous coupled flow and geomechanics. In this study, we find that the fault can be activated by water injection, when it is nearly critically stressed, being sensitive to small changes in stress. Lower cohesion, lower frictional angle, and higher injection rate can activate the fault more easily. Interestingly, the fault becomes activated away from the hydraulic fracture, before the injected water reaches the fault plane. Then, when the hydraulic fracture meets the fault plane, the injected water changes the effective stress of the fault significantly, causing large shear failure. We also calculate the magnitudes of the seismic moment, which are low, because only limited areas of the fault plane are failed. Thus, from this preliminary numerical study of Tarim Basin, we can possibly consider the fault activation as a reservoir stimulation technique for the Tarim Basin field.

The evapotranspiration (ET) is one of the most important factor in the hydrological cycle. In this study, remote sensing based ET algorithm using Moderate Resolution Imaging Spectroradiometer (MODIS) was considered. Then, Priestley-Taylor algorithm was used for estimation of potential evapotranspiration in South Korea, and its spatial distribution was analyzed. Overall applicability between estimated potential evapotranspiration and weather station pan evaporation in Nakdong river basin was represented. The results using small pan showed that correlation coefficient in Pohang and Moonkyung Station was 0.70 and 0.55, respectively. However, the results using large pan showed correlation coefficient in Pohang and Moonkyung Station was 0.62 and 0.52, respectively.

The AF track circuit that detecting train position and transmitting various train control data for DTG to the train on-board is composed of single operation system. If a failure occurs on this system, the driver should be operate the train by manually until the system is restored, because the system cannot control switch machines and signals by automatically. In this process the human error affects to the train delay, collision, derailment and critical safety accident. Therefore, this document has analyzed the effects that each failure mode influences on system and train, and quantified the failure valuation point and class. Basis on this quantified analysis result, MTBF increased and MTTR decreased and failure number also decreased by adopting the independent installation of power supply, the replacement of defected capacitors, the installation of resister cooling system and the improvement of maintenance methods. And the failure factors of AF track circuits were decreased by conducting the preventive maintenance which is a quantitative way of maintenance system by experience.

To achieve high performance in brain-computer interfaces (BCIs) using P300, most of the work has been focused on feature extraction and classification algorithms. Although significant progress has been made in such signal processing methods in the lower layer, the issues in the higher layer, specifically determining the stimulus schedule in order to identify the target reliably and efficiently, remain relatively unexplored. In this paper, we propose a systematic approach to compute an optimal stimulus schedule in P300 BCIs. Our approach adopts the partially observable Markov decision process, which is a model for planning in partially observable stochastic environments. We show that the thus obtained stimulus schedule achieves a significant performance improvement in terms of the success rate, bit rate, and practical bit rate through human subject experiments.

Trialkyltin n-Bu 3 SnH, an endocrine disruptor, was slowly converted by the catalytic action of group 4 Cp 2 MCl 2 /Red-Al (M = Ti, Zr, Hf) to produce two phases of products: one is an insoluble cross-linked solid, polystannane in 7-23%yield as minor product via redistribution/dehydrocoupling combination process, and the other is an oil, hexabutyldistannanein 69-90% yield as major product via simple dehydrocoupling process. Redistribution/dehydrocoupling process firstproduced a low-molecular-weight oligostannane possessing partial backbone Sn-H bonds which then underwent anextensive cross-linking reaction of backbone Sn-H bonds, leading to an insoluble polystannane. This is the first excitingexample of redistribution/dehydrocoupling of a tertiary hydrostannane catalyzed by early transition metallocenes.Key words : Redistribution, Dehydrocoupling, Polystannane, Metallocene, Catalyst, Endocrine 1. Introduction Inorganic polymers as substitutes for organic poly-mers are very important for diverse industrial applica-tions

Polymerization of vinyl monomers is promoted by thianthrene cation radical as a part of our research concerning the reactions of various agents with readily isolable, yet highly reactive species and elucidate the biological activity. Thianthrene cation radical initiated the homopolymerization and copolymerization of styrene and ethyl vinyl ether. The polymerization yields decreased as the concentration of phenylacetylene or diphenylethylene increased. Such polymereization by cationic thianthrene radical could provide some clues for the reaction in living animals. Comments on possible polymerization mechanisms were suggested.

The strain KCTC 11629BP, isolated from spontaneously fermented pine needle extract (FPE), showed fibrinolysis activity. The isolated strain was analyzed in physiological and biochemical experiments. Based on 16S rDNA sequencing and phylogenic tree analysis, the strain was identified to be a part of the genus Acetobacter, with Acetobacter senegalensis and Acetobacter tropicalis as the closest phylogenetic neighbors. Based on genotypic and phenotypic results, it was proposed that bacterial strain KCTC 11629BP represents a species of the genus Acetobacter. The strain was thusly named Acetobacter sp. FP1. In conclusion, Acetobacter sp. FP1 isolated from FPE possesses fibrinolytic activity.

The present study was to elucidate such a relationship by comparing the coronary risk factors with and without fatty liver adjusted for age and/or BMI. Study subjects were 665 women of 30 years and over, who underwent health package check-up at the health promotion center of an university hospital from July, 2009 to June, 2010. As a results, the prevalence rates of fatty liver of study subjects were 11.6%, and the rates were significantly higher in older age group, in the group of higher level of BMI. The group of subjects with fatty liver had significantly lower mean HDL-cholesterol and higher levels of body fat rate, TG, TC, LDL-cholesterol, FBS and ALT, then those parameters in subjects without fatty liver, even after adjustment for age and/or BMI. In age and BMI adjusted logistic regressions, The odds ratio of fatty liver was increased significantly as there is an increase in the abnormal group with TG, TC, LDL-C and ALT.

In this letter, we propose a cross-layer technique jointly considering modulation coding schemes (MCSs) of medium access control (MAC) layer, source significance information (SSI) and error concealment unit of application (APP) layer, and channel quality information (CQI) of physical (PHY) layer. We demonstrate the improved video quality by the proposed technique when H.264 videos are streamed over Rayleigh fading wireless channels.

In this thesis, the effect of switch maintenance improvement is confirmed after testing and operating the switch monitoring system that were researched and developed originally in order to improve method of electric switch maintenance. However, as in an automatic interlocking station where a ground crew was not placed, repair and inspection could not be carried out until the maintenance person comes in case of switch problems or maintenance. In order to improve this issue, control module was installed in a monitoring system which can communicate through a data radio to a remote computer. Thus, the monitoring device can receive control information which a remote computer commands during the operation of switches. Afterward, it shows information on the real-time status of swith, in particular, anomaly situation through user interface after the switch is operated. By improving performance of the monitoring system in this way which can be managed and controled at a remote place, the prompt countermeasure system in case of disruption will be built and as a result, efficiency and convenience of maintenance improvement will be expected to increase.

This study was performed to determine the levels of quality of life(QOL) according to the grade oflong-term care service in the elderly people who were judged from long-term care insurance, and to reveal its association with related variables. The interviews were made to 958 elderlies in urban and rural areas from March 1 to May 31, 2009. The mean scores of QOL among all subjects were 55.4±15.62(Grade Ⅰ; 49.7±14.17, Grade Ⅱ; 56.8±14.62, Grade Ⅲ; 59.4±16.36), and they were lower according to the higher grade of long-term care insurance. The multiple regression analysis was used to reveal the explanatory powers of factors influencing on the level QOL. Such factors as educational level, monthly income, subjective health status, depression and MMSE-K were shown to affect their QOL in Grade Ⅰ, Grade Ⅱ, and Grade Ⅲ with explanatory powers of 45~62%.Key Words : Quality of life, activity of daily living, depression, mental health, Elderly * 교신저자 : 조영채(choyc@cnu.ac.kr)접수일 10년 08월 26일 수정일 10년 10월 14일 게재확정일 10년 10월 15일

The LOD data sets consist of RDF Triples based on the Ontology, a specification of existing facts, and by linking them to previously disclosed knowledge based on linked data principles. These structured LOD clouds form a large global data network, which provides a more accurate foundation for users to deliver the desired information. However, it is difficult to identify that, if the presence of the same object is identified differently across several LOD data sets, they are inherently identical. This is because objects with different URIs in the LOD datasets must be different and they must be closely examined for similarities in order to judge them as identical. The aim of this study is that the prosed model, RILE, evaluates similarity by comparing object values of existing specified predicates. After performing experiments with our model, we could check the improvement of the confidence level of the connection by extracting the link value.

본 연구는 공무원들의 스트레스나 피로수준과 같은 사회심리적 건강상태가 그들의 직급, 근무경력 등의 직업관련 특성이나 업무요구도, 업무자율성, 직장 내에서의 사회적 지지와 같은 직무스트레스 내용에 의해 영향을 받고 있는지를 구조방정식모형을 통하여 검토하고자 시도하였다. 연구대상은 대전광역시의 5개 정부 공공기관에 근무하는 일반 사무직 행정공무원 805명이었으며, 자료 수집은 2009년 10월 1일부터 11월 30일까지의 기간 동안에 표준화된 자기기입식 설문지(self-administered questionnaire)를 사용하여 실시하였다. 연구결과, 공무원들의 스트레스 및 피로수준은 직급, 근무경력, 업무만족도, 업무자율성, 상사의 지지도 및 동료의 지지도와는 유의한 음의 상관관계를 나타낸 반면, 년 간 결근일수, 업무요구도와는 유의한 양의 상관관계를 나타내었다. 구조방정식모형 분석 결과 연구대상자들의 직무스트레스 요인은 직업관련 특성 요인보다 사회심리적 건강상태에 더 큰 영향을 미쳤으며, 직무스트레스가 높을수록 사회심리적 건강상태를 나타내는 스트레스와 피로수준을 높여주는 것으로 나타났다. 한편, 직업관련 특성의 인지정도가 높을수록 직무스트레스 요인을 감소시키는 효과가 있는 것으로 나타났다. 따라서 공무원들의 스트레스나 피로를 감소시키기기 위해서는 직업관련 특성에 따른 직무내용의 개선을 위한 프로그램의 개발 및 시행이 필요할 것으로 생각된다. 【The effects of job related factors on psychosocial health status were examined by taking job stress into account. The self-administered questionnaires were performed, during the period between Oct. 1st, 2009 and Nov. 30th, 2009, to 805 individuals in the service of general administration located in Daejeon City. Causal relationships between job related factors, job stress, and, psychosocial health status were examined by structural equation model. The main finding as follows: For correlations of such indices of psychosocial health status as PWI and MFS with various studied items, all of these two indices were found to be in a negative correlation with the job position, job career, satisfaction in job life, autonomy of job, supervisors support and coworkers support, whereas in positive correlation with the experience of sick absence per year and job demand. With the analysis of structural equation model, the degree of job stress factors was more influential on the level of psychosocial health status than job related factors in such a manner as that the greater the job stress, while the lower the job related factors, the higher the psychosocial health status(PWI and MFS). Moreover, it was found to have the inter-relational effects that the greater the job related factors, the lower the job stress factors. Thus the effective strategy for stress and fatigue symptoms reduction among governmental employees requires additional programs focusing on innovated job specifications.】

The train control system used in Gyeongbu-line is classified in ATC, IXL and CTC. The ATC data related to speed and space control for trains are transmitted from wayside to onboard by way of UM71 AF track circuits and BSP Loop. The information transferred by track circuits is composed of operation data which directly influence to the train operation and the information transferred by BSP Loop is used in the section which requires the additional data transmission about the particular track-side environment such as tunnel, hot box detector or insulated section. In this paper, for the BA type turning unit of the UM71 AF track circuits which is mainly used in the linking section of existing and high-speed lines from the opening of the Gyeongbu line till the present, we not only analyze the characteristics of BA but also compare and analyze baseline values and the measured values. With this analysis, we will be able to propose how to solve the problems about operation and maintenance such as track circuit malfunctions of the relevant sections.

In this paper, we study the communication based train control technology which has been improved for the railroad operation efficiency. All the signalling systems currently used in Korea are track circuit based train control systems, which train mobility and safety are considered on. When it comes to the recent abroad trend, development for communication based train control system, which arises new paradigm in the field of high density train separation, have been promoted. Considering the urgent necessity to develop the above mentioned technology, we would like to propose the research and development of communication based train control system and the present domestic and foreign statuses of on-board equipment development. In this paper, therefore, we had been developed localization on-board equipment of communication based train control system, which is the key construction of train control systems. For its verification, we accomplished installation and yard test on-board equipment of communication based train control system on Bundang-line`s EMU(Electrical Multiple Unit).

As touch based input becomes more popular in mobile devices, there is an increasing need for haptic feedback on key-less input surface. Four experiments were conducted to design and evaluate identifiable emulated key-click signals using a piezoelectric actuator. Experiments I and II assessed the information transmission capacity for the amplitude, frequency, and number of cycles of raised cosine waveforms used to drive the piezo actuators under fixed- and roving-background conditions, respectively. Experiment III estimated the total information transfer for all three parameters. The results were used to reduce the number of stimulus alternatives in the key-click signal set with the goal to achieve perfect identification performance. Experiment IV verified that up to 5 to 6 identifiable key-click signals could be achieved with the experimental setup. The present study outlines an information theoretic approach to conducting identification experiments to guide the design of and to evaluate a perfectly identifiable stimulus set. The methodology can be applied to other applications in need of perceptually identifiable stimulation patterns.

The effect of contact location information on virtual edge perception was investigated in two experiments. In Experiment 1, participants discriminated edge sharpness under force-alone and force-plus-contact-location conditions using a 4.8 mm radius contact roller. Virtual objects were 2D profiles of edges with two adjoining surfaces. For both conditions, the Just Noticeable Difference (JND) in change of edge radius increased from 2.3 to 7.4 mm as edge radii increased from 2.5 to 20.0 mm; there was no significant difference between the two conditions. A follow-up experiment with contact location alone resulted in higher edge sharpness JNDs. In Experiment 2, the same edge sharpness discrimination task was performed using a smaller contact roller (R = 1.5 mm) to investigate the effect of roller size. The JNDs for the smaller roller were not statistically significant from those of the larger roller. Our results suggest that 1) contact location cues alone are capable of conveying edge sharpness information, but that force cues are dominant when both types of cues are available; and 2) the radius of the contact roller does not significantly affect the user's ability to discriminate edge sharpness, indicating that the participants could use the changes in contact location to judge curvature.

Pine needle extract (PE) and fermented pine needle extract (FPE) have been reported to show various biological and pharmacological activities such as antioxidant, anti-inflammatory, anti-bacterial, anti-cholesterol, gastrointestinal motility control, and fibrinolytic effect. The aims of our research were to isolate fibrinolytic compounds from PE and FPE and evaluate their antithrombotic activity in vitro and in vivo. Protocatechuic (1) and shikimic (2) acids were isolated and identified from FPE. 1 and 2 not only have fibrinolysis activity but also inhibit fibrin formation similar to aspirin. Lysis of fibrin clots by 1 and 2 occurred completely at pH 2-4. Results of SDS-PAGE showed that fibrin polypeptide chains (Aα, Bβ, γ) lysed by 1 and 2 were intact. The antithrombotic effects of 1 and 2 were confirmed by models of carrageenan-induced tail thrombosis, collagen and epinephrine-induced pulmonary thromboembolism in mice, and FeCl3-induced carotid arterial thrombus. Moreover, 1 and 2 did not induce hemorrhage in the tail veins of mice, unlike common antithrombotic compounds. We also measured changes in the quantities of 1 and 2 obtained from FPE. As fermentation progressed, we demonstrated that the quantity of 1 steadily increased, while the quantity of 2 did not significantly change. We therefore demonstrated that FPE is an excellent resource for 1 and 2 and can be produced inexpensively in sufficient quantities for industrial-scale extraction.

We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when β (plasma pressure/magnetic field pressure) is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad’s work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β. This represents critical progress toward an understanding of the plasma dynamics in a high-β cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

We describe a program to demonstrate the scientific basis of magnetized target fusion (MTF). MTF is a potentially low-cost path to fusion which is intermediate in plasma regime between magnetic (MFE) and inertial fusion energy (IFE). MTF involves the compression of a magnetized target plasma and pressure times volume (PdV) heating to fusion relevant conditions inside a converging flux conserving boundary. We have chosen to demonstrate MTF by using a field-reversed configuration (FRC) as our magnetized target plasma and an imploding metal liner for compression. These choices take advantage of significant past scientific and technical accomplishments in MFE and defense programs research and should yield substantial plasma performance (n/spl tau/>10/sup 13/ s-cm/sup -3/ T>5 keV) using an available pulsed-power implosion facility at modest cost. We have recently shown the density, temperature, and lifetime of this FRC to be within a factor of 2-3 of that required for use as a suitable target plasma for MTF compression for a fusion demonstration.

Ethylene (C2H4) on the Si(0 0 1) surface has been a subject of numerous investigations over a decade. Despite a wealth of experimental and theoretical studies, the adsorption structures are not clearly understood yet. In order to elucidate this controversial issues clearly, C2H4 molecules have been non-dissociatively chemisorbed on Si(0 0 1)-(2 × 1) surface at room temperature with an exposure of 100 L, and C2H4 on Si(0 0 1) surface structure has been investigated by coaxial impact collision ion scattering spectroscopy (CAICISS). To determine the adsorption structure of the C2H4 molecules definitely, the computer simulation with the two-dimensional trajectory counting method has been performed for the recently proposed most possible two single molecular adsorption configurations (di-σ on-top and di-σ end-bridge). The CAICISS spectra show a better agreement with the simulation results for the di-σ on-top structure than that for the di-σ end-bridge structure. The bond length of Si dimer separation on the Si(0 0 1) surface with the adsorption of 100 L C2H4 is found to be 2.35 ± 0.05 A. This implies that the bonding of Si dimers stays intact. It is also found that the bonding length of C–Si and C–C is 1.81 ± 0.05 A and 1.61 ± 0.05 A respectively.

Theoretical works by Barnes and Nebel [R. A. Nebel and D. C. Barnes, Fusion Technol. 38, 28 (1998); D. C. Barnes and R. A. Nebel, Phys. Plasmas 5, 2498 (1998)] have suggested that a tiny oscillating ion cloud may undergo a self-similar collapse in a harmonic oscillator potential formed by a uniform electron background. By tuning the external radio-frequency electric fields to this naturally occurring mode, it is then possible to heat the ions to obtain very high densities and temperatures simultaneously during the collapse phase of the oscillation through adiabatic compression. However, a major uncertainty in this oscillating plasma scheme is the dynamics and stability of the background electrons in the virtual cathode. Recent work based on the electron fluid equations have demonstrated that the required electron cloud is susceptible to an instability that is analogous to the Rayleigh–Taylor mode present in fluid mechanics [R. A. Nebel and J. M. Finn, Phys. Plasmas 8, 1505 (2001)]. This paper describes an...

The atomic structure of Cs atoms adsorbed on the Si(0 0 1)(2 × 1) surface has been investigated by coaxial impact collision ion scattering spectroscopy. When 0.5 ML of Cs atoms are adsorbed on Si(0 0 1) at room temperature, it is found that Cs atoms occupy a single absorption site on T3 with a height of 3.18 ± 0.05 A from the second layer of Si(0 0 1)(2 × 1) surface, and the bond length between Cs and the nearest Si atoms is 3.71 ± 0.05 A.

A "plasma decon chamber" has been developed at Los Alamos National Laboratory (LANL), Albuquerque, NM, to study the decontamination of chemical and biological warfare agents. This technology is targeted at sensitive electronic equipment for which there is currently no acceptable, nondestructive means of decontamination. Chemical reactivity is provided by a downstream flux of reactive radicals such as atomic oxygen and atomic hydrogen, produced in a capacitively coupled plasma. In addition, the decon chamber provides an environment that accelerates the evaporation of chemical agents from contaminated surfaces by vacuum, heat, and forced convection. Once evaporated, agents and agent byproducts are recirculated directly through the plasma, where they undergo further chemical breakdown. Preliminary studies on actual chemical agents were conducted at the U.S. Army Dugway Proving Ground, Dugway, UT. Exposures were conducted at a system pressure of 30 torr, exposure temperature of 70/spl deg/C, plasma-to-sample standoff distance of 10 cm, and 10% addition of oxygen or hydrogen to a helium balance. This exposure condition was based on optimization studies conducted at LANL on agent simulants. The agents studied were VX and soman (GD) nerve agents and sulfur mustard (HD) blister agent, as well as a thickened simulant. All agents were decontaminated off aluminum substrates to below the detection limit of /spl sim/0.1% of the initial contamination level of approximately 1 mg/cm/sup 2/. For VX, this level of decontamination was achieved in 8-16 min of exposure, while only 2 min were required for the more volatile HD and GD. Evaporation and subsequent gas-phase chemical breakdown in the plasma appears to be the dominant decontamination mechanism for all of the agents. However, an observed difference in the decontamination process between oxygen and hydrogen indicates that chemical reactivity in the liquid phase also plays an important role.

Processing materials at atmospheric pressure provides clear advantages over traditional, vacuum-based plasma processing: in addition to reduction in the capital cost of equipment and the elimination of constraints imposed by vacuum-compatibility, high pressure and low temperature plasma processes offer unprecedented improvements for generation of active chemical species, high chemical selectivity, minimal ion densities resulting in low surface damage and surface treatment methods unattainable by other means. We describe several variations of this unique plasma source and some of its potential applications.

Gas breakdown is studied in an atmospheric pressure rf capacitive plasma source developed for materials applications. At a rf frequency of 13.56 MHz, breakdown voltage is largely a function of the product of the pressure and the discharge gap spacing, approximating the Paschen curve. However, breakdown voltage varies substantially with rf frequency due to a change in the electron loss mechanism. A large increase in breakdown voltage is observed when argon, oxygen, or nitrogen is added to helium despite their lower ionization potential. Discussion is given for optimal breakdown conditions at atmospheric pressure.

The reaction chemistry in the afterglow of a non-equilibrium, capacitive discharge, operated at 600 Torr total pressure with (0.5 to 5.0) × 1017 cm-3 of oxygen in helium, has been examined by ultraviolet absorption spectroscopy, optical emission spectroscopy, and numerical modeling. The densities of the active species, O(3P), O2(1Δg), O2(1Σg+), and O3, have been determined as a function of the operating conditions. At RF power densities between 6.1 and 30.5 W/cm3 and a neutral temperature of 100 ± 40 °C, the plasma generated (0.2 to 1.0) × 1016 cm-3 of O(3P) and O2(1Δg), (0.2 to 2.0) × 1015 cm-3 of O2(1Σg+), and (0.1 to 4.0) × 1015 cm-3 of O3. After the power was turned off, the singlet-sigma and singlet-delta states decayed within 0.1 and 30.0 ms, respectively. The concentration of oxygen atoms remained constant for about 0.5 ms, then fell rapidly due to recombination with O2 to form O3. It was found that the etching rate of polyimide correlated with the concentration of oxygen atoms in the afterglow, in...

Neutral bremsstrahlung emission spectrum is measured in an atmospheric-pressure radio frequency (rf) capacitive discharge for a gas mixture of helium (99.5%) and oxygen (0.5%) using a high resolution triple monochromator between 450 and 1000 nm. Good agreement is obtained for spectral variation and absolute intensity between the observed neutral bremsstrahlung and theoretical emissivity calculated using electron–neutral momentum cross sections. Based on a theoretical fitting, the discharge is characterized by a time averaged electron density of 2.9×1011 cm−3 and an electron temperature of 1.9 eV for an input power density of 28 W/cm3.

The atmospheric pressure plasma jet (APPJ) [A. Schutze et al., IEEE Trans. Plasma Sci. 26, 1685 (1998)] is a nonthermal, high pressure, uniform glow plasma discharge that produces a high velocity effluent stream of highly reactive chemical species. The discharge operates on a feedstock gas (e.g., He/O2/H2O), which flows between an outer, grounded, cylindrical electrode and an inner, coaxial electrode powered at 13.56 MHz rf. While passing through the plasma, the feedgas becomes excited, dissociated or ionized by electron impact. Once the gas exits the discharge volume, ions and electrons are rapidly lost by recombination, but the fast-flowing effluent still contains neutral metastable species (e.g., O2*, He*) and radicals (e.g., O, OH). This reactive effluent has been shown to be an effective neutralizer of surrogates for anthrax spores and mustard blister agent. Unlike conventional wet decontamination methods, the plasma effluent does not cause corrosion and it does not destroy wiring, electronics, or mo...

A plasma jet has been developed for etching materials at atmospheric pressure and between 100 and C. Gas mixtures containing helium, oxygen and carbon tetrafluoride were passed between an outer, grounded electrode and a centre electrode, which was driven by 13.56 MHz radio frequency power at 50 to 500 W. At a flow rate of , a stable, arc-free discharge was produced. This discharge extended out through a nozzle at the end of the electrodes, forming a plasma jet. Materials placed 0.5 cm downstream from the nozzle were etched at the following maximum rates: for Kapton ( and He only), for silicon dioxide, for tantalum and for tungsten. Optical emission spectroscopy was used to identify the electronically excited species inside the plasma and outside in the jet effluent.