Dead Spots Research Articles

Improvement of Field-Emission Characteristics of Carbon Nanotubes by Post Electrical Treatment

The field-emission characteristics of carbon nanotubes (CNTs), such as uniformity and brightness, were improved by electrical treatment using nonstationary electric fields between the cathode of screen-printed CNT emitters and the anode of a phosphor-coated indium-tin-oxide glass substrate in diode configuration. Dead or weak emission spots, where almost no emission of electrons was observed, started to emit electrons by applying an alternating-current voltage to the cathode electrode and a constant voltage to the anode electrode. The nonstationary electrical treatment was more effective than the direct-current (dc) and the square-pulsed electrical treatments for the emission uniformity and brightness. It was found that the nonstationary electrical treatment not only activated CNT emitters but also suppressed abnormally high emission spots without the drawbacks of electrical breakdown. Consequently, more than 1.8 and 1.3 times improvements of emission uniformity and brightness, respectively, were obtained after the treatment, when compared with the dc electrical treatment for the same amount of emission currents and the same duration of the treatments. Therefore, the method can be effectively applied to field-emission devices based on CNTs for the enhancement of emission properties.

GETA sandals: a footstep location tracking system

This paper presents the design, implementation, and evaluation of a footstep based indoor location system. The traditional Japanese GETA sandals are equipped with force, ultrasonic, orientation, RFID sensors and an accelerometer to produce a wearable location tracking system that demand little infrastructure in the deployed environment. In its basic form, a user simply puts on GETA sandals to enable tracking of his/her locations relative to a starting point (e.g., a building entrance), making it easy for deployment everywhere. The footstep location system is based on dead-reckoning, which works by measuring and tracking displacement vectors along a trail of footsteps. Each displacement vector is formed by drawing a line between each pair of footsteps, and the position of a user can be calculated by summing up the current and all previous displacement vectors. Unlike most existing indoor location systems, the footstep based method does not suffer from problems with obstacles, multi-path effects, signal noises, signal interferences, and dead spots. There are two technical challenges in the proposed design: (1) location error accumulates over distance traveled, and (2) displacement measurements are sporadic during stair climbing. The first problem is addressed by a light RFID infrastructure, while the second problem is remedied by incorporating an accelerometer into the system. Experiments on GETA prototype are conducted to evaluate the positional accuracy of our system.

Downlink performance and capacity of distributed antenna systems in a multicell environment

Distributed antenna systems (DAS) have been widely implemented in state-of-the art cellular communication systems to cover dead spots. Recent academic studies have shown that in addition to coverage improvements, DAS can also have potential advantages such as reduced power and increased system capacity in a single cell environment. This paper analytically quantifies downlink capacity of multicell DAS for two different transmission strategies: selection diversity (where just one or two of the distributed antennas are used) and blanket transmission (where all antennas in the cell broadcast data). Simple repeaters are a special case of our analysis. A generalized information theoretic analysis is provided to illuminate the fundamental limits of such systems in the cellular context. The results show that DAS reduces other-cell interference in a multicell environment and hence significantly improves capacity (by about 2x), with particularly large improvements for users near cell boundaries. Less obviously, from a communication theory standpoint, it is shown that selection diversity is preferable to blanket transmission in terms of achievable ergodic capacity. For blanket transmission, we show that the optimal transmission strategy is just phase steering due to the per antenna module power constraints in DAS

Threshold Functions, Node Isolation, and Emergent Lacunae in Sensor Networks

A geometrically random network of sensors is obtained by modeling sensors as random points in the unit disc equipped with a local sensing capability and the ability to communicate with other sensors in their vicinity. Node extinctions in the network representing the finite battery lifetimes of the sensors are modeled as a sequence of independent random variables governed by a common probability distribution parametrized by the sensing and communication radii of the sensor nodes. Following its establishment, the devolution of the network with time is characterized by the appearance first of isolated nodes, then the growth of sensory lacunae or dead spots in the sensor field, and, eventually, a breakdown in connectivity between survivors. It is shown that these phenomena occur very sharply in time, these phase transitions occurring at times characteristic of the underlying probability law governing lifetimes. More precisely, it is shown that as the number of sensors grows there exists a critical point in time determined solely by the lifetime distribution at which the number of emergent lacunae of a given size is asymptotically Poisson

Measurements and Characterization of Ultra Wideband Propagation Channels in a Passenger-Car Compartment

Ultra wideband (UWB) signal propagation was measured and characterized in comparison with narrowband in a passenger-car compartment, to accommodate the design of new wireless devices for the safety and comfort of passengers. Spatial distributions of UWB and narrowband path gain, delay profiles, and delay spreads within the compartment were derived from frequency-domain responses (from 3.1 to 10.6 GHz) measured with a vector network analyzer. Whereas narrowband channels resulted in a number of dead spots (deep fading points), UWB yielded none, though some frequency dispersion was inevitable. Fading depth versus occupied bandwidth was also derived, which indicated superiority of UWB over narrowband systems from the viewpoint of link budget. Comparison with two other environments was also made in the received energy contained in a given number of multipath components.

The Acoustical Performance Analysis of Bilkent Amphitheater: Proposal for Acoustical Renovation

The 4000 seat multi-purpose Bilkent Amphitheater is a semi-closed amphitheater with a volume of 90,000 m3, designed to serve the University's and the city's educational and artistic activities. At the beginning, the amphitheater was designed only for open-air performances. Afterwards it was decided it would be roofed with a tensile membrane in order to protect the spectators from atmospheric effects. However, the covered amphitheater was turned into a resounding and a problematic place with a reverberation time of more than 6 s. when the hall is unoccupied. Acoustical interventions were implemented, but these have not been sufficient in decreasing the number of problematic echoes and dead spots. This paper analyzes the hall by means of assessing the fundamental acoustical parameters for both speech and music. Parameters such as reverberation time, early decay time, clarity, definition, lateral fraction, strength and speech transmission index were calculated by the aid of ODEON Room Acoustics Program simulation software Version 6.01. It was observed that most of the parameters are out of the optimum range, and that the sound focused strongly in some locations. After further acoustical renovation of the hall, the distribution of sound became more homogenous as measures of most of the parameters fell into reasonable ranges.

Silicon/graphite composites as an anode material for lithium ion batteries

Mixed silicon–graphite composites have been prepared by means of mechanical milling process. Their micro-heterogeneous structure is considered responsible for electrode failures. A fingerprint of this process is seen by cycling the carbonaceous component of the composite in an electrolyte containing small amount of propylene–carbonate (PC). Local voltage drops close to 0 V (versus Li metal) resulted in local electrode mechanical deterioration. In the presence of silicon particles such local disorders would lead to a loose interparticle contact (zones called dead spots). Deterioration pattern of the mixed composite electrode may be considered as a set of ‘dead spots’ spreading across the electrode as the cycling proceeds. Hence, a careful optimization is necessary in order to fabricate composite electrode giving minimum local disorders and having satisfactory cycling performance.

The Annihilated Self

The Annihilated SelfMichael EigenMichael Eigen1. 225 Central Park West, #101A New York, NY 10024Search for more papers by this authorPublished Online:March 2006https://doi.org/10.1521/prev.2006.93.1.25PDFPDF PLUS ShareShare onFacebookTwitterLinkedInRedditEmail ToolsAdd to favoritesDownload CitationsTrack Citations About Previous article Next article FiguresReferencesRelatedDetails Cited byCited by1. ErratumOnline publication date: 12 February 2018. Go to citation Crossref Google Scholar2. Beyond Sexuality, Beyond Perversion: The Annihilated Last ScreamOnline publication date: 30 August 2017. Go to citation Crossref Google Scholar3. Containment, Holding, and ReceptivityOnline publication date: Go to citation Crossref Google Scholar4. Contenir, soutenir et être réceptifOnline publication date: Go to citation Crossref Google Scholar5. Contenir, soutenir et être réceptifOnline publication date: Go to citation Crossref Google Scholar6. The “Voice” of Breakdown: On Facing the Unbearable Traumatic Experience in Psychoanalytic WorkOnline publication date: 8 March 2016. Go to citation Crossref Google Scholar7. Morality, Selflessness, Transcendence: On Treatment Goals of a Spiritually Sensitive PsychoanalysisOnline publication date: 18 September 2015. Go to citation Crossref Google Scholar8. Patient-Analyst “Withness”: on Analytic “Presencing,” Passion, and Compassion in States of Breakdown, Despair, and DeadnessOnline publication date: 19 September 2017. Go to citation Crossref Google Scholar9. The autistic core in Aboriginal trauma: Breaking down or breaking out of the autistic defenceOnline publication date: 22 November 2012. Go to citation Crossref Google Scholar Volume 93Issue 1Feb 2006 Information© N.P.A.P.PDF download

Evaluation of a Hands-Free Wireless Communication Device in the Perioperative Environment

The objective of this study was to evaluate the efficiency and reliability of a hands-free voice over Internet protocol (VOIP) communication system in the perioperative environment. Two surveys were administered to anesthesiologists and operating room (OR) nurses working at an academic medical center. Providers were queried by alphanumeric pages or VOIP queries during OR work shifts to measure communication response times. Providers, responding to the query, were asked to verbally complete a system performance survey to capture information regarding their workload and work environment at the time of the query. A user feedback survey was independently administered in writing to a convenience sample of OR providers to obtain information regarding provider communication preferences, concerns, and recommendations. OR providers responded to communication queries four times faster when using VOIP compared to alphanumeric pagers. Providers found VOIP to be much less reliable than conventional pager-telephone systems. Dead spots in the 802.11b network and errors in speaker recognition were frequently cited as sources of system failures. Providers also expressed concern in maintaining confidentiality of patient data or other clinical data communicated using this system. The results of this study suggest that VOIP is still a developing technology but one that is currently viable in the clinical setting. The technology can be used efficiently and securely in health care if users are given the proper training its functions and capabilities.

Chemical Bloom Thinning Hybrid Grape Cultivars

Abstract Caustic chemicals (Endothall, Wilthin and ammonium thiosulfate) were applied at bloom to French-American hybrid grape cultivars (‘Seyval blanc’, ‘Vidal blanc’, and ‘Chambourcin’) to evaluate their potential as chemical thinners. The chemicals caused phytotoxicity to leaves and clusters resulting in brown, dead spots on leaves and brown areas of the clusters. Injury symptoms increased as concentration of Endothall increased. ‘Vidal blanc’ was the most sensitive cultivar to Endothall and ‘Chambourcin’ was the most sensitive to ammonium thiosulfate (ATS). Hand cluster thinning at bloom consistently increased cluster weight, berry number per cluster, juice soluble solids and pH and decreased cluster number and yield of all cultivars with the exception that yield of ‘Seyval blanc’ was reduced only one year. Generally as concentration of Endothall increased, thinning increased. Endothall at 1.92 ml-L-1 caused reductions in yield and increases in juice soluble solids and pH that were very similar to han...

Fungal Pathogens Associated with Blueberry Propagation Beds in North Carolina

SUMMARY Death of blueberry cuttings in commercial rooting beds was observed due to abiotic and biotic causes. Abiotic causes included poor watering practices, water quality, rooting medium, and inadequate drainage due to poor rooting bed design. Biotic causes were attributable to fungi and included (1) non-pathogenic Basidiomycetes colonizing unsterilized rooting media, (2) airborne or rain-splashed pathogens infecting individual cuttings (Botryosphaeria, Pestalotia and other sp.), and (3) Cylindrocladium sp. that spread radially from the initial infection, producing circular dead spots in rooting beds. Re-use of Cylindrocladium-infested media resulted in complete loss of cuttings. Methyl bromide fumigation was successfully used to sanitize infested media.

Effect of body shape on vibration of electric guitars

The body vibrations of an electric guitar are typically ignored since the string vibrations are converted to sound through the use of a magnetic pickup. However, vibrations in the neck have been shown to cause dead spots at certain fret positions [H. Fleischer, J. Acoust. Soc. Am. 105, 1330 (1999)]. In this paper we compare the vibrational mode shapes and frequencies of three electric guitars with different body shapes. Two guitars are solid-body electrics: one with a body shape which is symmetric about the neck axis (Epiphone Coronet) and the other which is not (Gibson Explorer). Mode shapes and frequencies are considerably different for the body, though neck vibrations are more closely related. The third guitar is an arched top hollow-body electric (Gibson ES-335). For this guitar, the top and back plates and the air cavities may also contribute to the guitar sound quality. Mode shapes and frequencies are determined from experimental modal analysis using an impact hammer and accelerometer.

Arrangement of aerators in an intensive shrimp growout pond having a rectangular shape

Simulations have been conducted to suggest general principles for the arrangement of aerators within a rectangular pond used for the growout of marine shrimp such as Penaeus monodon and Penaeus japonicus. Computational fluid dynamic models were produced for three schemes that were identified in a survey of Australian Prawn Farming Association members. These arrangements are ‘in-line’ (series), ‘parallel’ (side by side), and ‘diagonal’ (diverting apart). Model results were assessed on the basis of benthic shear stress by classifying regions of pond bottom as ‘red zone’ (excessive stress), ‘green zone’ (desirable), and ‘dead spots’ (sediment traps). A comparison of results indicates that conventional aerators should be arranged diagonally or in parallel. It is also apparent that low-speed operation would be advantageous. These recommendations are consistent with the long-established practice of establishing pond-wide circulation.

A non-contact vital signs monitor.

The expansion and contraction of the lungs and heart result in movement of the chest wall that can be detected and monitored to determine respiration and heart rate. A prototype non-contact Vital Signs Monitor (VSM) has been developed which uses very low power, high frequency Doppler radar to detect these motions. Digital signal processing (DSP) techniques, imbedded in the VSM, are used to extract heart and respiration rate information from the resultant waveform. A 10-GHz prototype VSM was developed for the Air Force in the mid-1980s using analog technology. The objective was to assess a fallen soldier's clinical condition at distances up to 100 meters before committing resources to assist that individual. An updated and improved version of the original VSM was developed in 1997. This device was designed to operate at shorter distances, use a higher frequency carrier, and provide more specific heart and respiration rate information using digital signal processing techniques. The VSM radar system is a straightforward homodyne receiver. It operates using frequency modulated continuous wave (FM-CW) transmission, which allows for very low power levels. The safe human power density exposure level at its operating frequency of 35 GHz is 10 mW/cm2. A simple approximation using uniform distribution and an antenna aperture of 2 cm by 3 cm gives a power density at the antenna face of 0.017 mW/cm2, nearly a factor of 1000 below the safe level. When the VSM's antenna is trained on the chest wall of a subject, the VSM is capable of measuring and distinguishing minute movements resulting from the mechanical activity of the heart and lungs. As the subject's chest wall moves, the exact phase of the return signal changes. To avoid the possibility of phase-related dead spots, two signals differing in phase by 90 degrees are used to demodulate the signal to baseband (DC). The two resulting "time-varying DC" signals represent the sine and cosine of a phase angle corresponding to the changing position of the target, in this case the motion of the chest wall. The current VSM operates at a frequency of 35 GHz with a corresponding wavelength of only 8.6 mm. This provides a response sensitive enough to detect the small motions caused by cardiac function. The Vital Signs Monitor has several possible application areas. The fact that it is noncontacting would make it especially attractive for monitoring patients in burn units, NICUs, or trauma centers, where attaching electrodes is either inconvenient or not feasible. Results to date indicate a strong correlation between the cardiac component of the motion signal and an electrocardiogram (ECG). With careful signal processing and analysis, it may be possible to extract clinically useful information about cardiac condition, function, or performance from the surface-motion waveform. This could provide a safe, inexpensive, and painless addition to the diagnostic and monitoring tools currently available to cardiologists. Although there are technical obstacles to overcome in filtering gross motions of the subject, the VSM offers significant advances over conventional methods of measuring heart and respiration rate.

Diagnosing dead spots of electric guitars and basses by measuring the mechanical conductance

The ‘‘sustain’’ of the string signal is considered as a quality attribute of an electric plucked instrument. In musical practice, distinct locations are observed on the fretbroad where a string decays faster than at adjacent frets. Such ‘‘dead spots’’ originate from the fact that the string may cause the neck to vibrate. Energy flows from the string to the neck with the consequence that the string vibration decays irregularly fast. Experiments were performed with the aim of finding a measuring approach for the diagnosis of dead spots in terms of the vibration willingness of the neck. Various parameters (decay rate, surface velocity, admittance) were ascertained for a series of electric guitars and basses. Special care was taken to ensure comparable and ‘‘natural’’ boundary conditions. Measuring the mechanical conductance (i.e., the real part of the point admittance) on the neck with the instrument held in normal playing position proved a straightforward and reliable method for the diagnosis of dead spots. The measuring procedure and instrumentation will be presented. Typical results will be given in a compact 3-D representation (conductance versus frequency for each fret), evaluated and related as well to the decay rates as to the vibrations of the instrument body.

Spring Dead Spot of Buffalograss Caused by Ophiosphaerella herpotricha in Kansas and Oklahoma.

Buffalograss (Buchloe dactyloides) is widely planted in the Great Plains region of the United States as an amenity turfgrass. In May 1993, we observed circular dead spots in buffalograss lawns that were resuming growth following winter dormancy. The dead spots, 12 to 40 cm in diameter, were slowly filled in by buffalograss during the summer but reappeared in the same locations the following spring. Roots and stolons at the patch margins were colonized by darkly pigmented, ectotrophic fungal hyphae. Ophiosphaerella herpotricha, a cause of spring dead spot disease of bermudagrass (Cynodon spp.), was consistently isolated from diseased buffalograss roots collected in Kansas and Oklahoma. Identification of O. herpotricha was confirmed by the use of species-specific polymerase chain reaction (PCR) primers. To complete Koch's postulates, a 3-year-old stand of buffalograss cv. Sharp's Improved located in Manhattan, KS, was inoculated in September 1994 with O. herpotricha. Eleven soil cores, 10 cm in diameter × 8 cm deep, were removed at 1.2-m intervals across the turf. Five grams of oat seed infested with O. herpotricha (isolate KS221) wasadded to each hole and the soil plug was reinserted. For controls, 5 g of sterile oat seed was inserted in the bottom of each of 11 additional holes. No symptoms developed the following spring, but circular dead spots, ranging in size from 18 to 43 cm in diameter, were observed at 10 of 11 and 6 of 11 inoculation sites in May 1996 and 1997, respectively. No spots were noted in areas amended with sterile oats. O. herpotricha was consistently isolated from the roots at the margins of the patches. This is the first report of O. herpotricha causing spring dead spot in buffalograss.

Experimental study on distributive mixing characteristics of a new type of pin mixing section

AbstractTo eliminate two shortcomings of normal pin mixing sections, namely, the lack of efficient mixing mechanisms and the formation of dead spots, a new type of pin (pins channeled from top‐front to bottom‐rear) was previously proposed. As an experimental verification of the effectiveness of this type of pin, a dye decoloration experiment with a visual single screw extruder was carried out. The comparative experiments show that a “//” type pin mixing section (the orientation of holes in the pins is parallel) has the best mixing ability; a 45° angle between the projected line of orientation of holes in the pins and the screw axial line provides maximum mixing; however, a 45° angle between the orientation of the pin array and the screw axial direction results in poor mixing. The effect of density of the pins along the screw circumferential and axial direction on distribution mixing was also investigated experimentally.

Design of a new type of pin mixing section for a screw extruder based on analysis of flow and distributive mixing performance

A new type of pin to be installed in the mixing section of a screw extruder is proposed based on the results of numerical calculation of flow field and local and integral mixing efficiency in the cross-section of a pin mixing section. Two problems presented in general by pin mixing sections, i.e. the lack of efficient mixing mechanisms and the formation of dead spots, can be solved by channeling pins from top-front to bottom-rear. The calculated results of local mixing efficiency indicate the location of regions of good or poor mixing in the cross-section of the mixing section, and the integral mixing efficiency provides the means to compare the mixing performance of different mixing sections. The experimental results of flow visualization and mixing pattern agreed well with those obtained from numerical calculations, thus supporting the validity of the theoretical analysis. Even though the study was confined to the cross-section, it has directive significance in the practical design of pin mixing sections in the light of the theory of distributive mixing.

Analytical Study on Flow and Distributive Mixing of a New Type Pin Mixing Section for Screw Extruder

Abstract A new type of pin to be installed in mixing section of screw extruder is proposed based on the results of numerical calculation of flow field and local mixing efficiency. Two problems presented in general pin mixing section, i.e., the lack of randomization in mixing mechanism and the formation of dead spots, can be solved through diagonally-channeling pins from top to bottom. From the results of numerical analysis of local mixing efficiency it is known that in the cross-section of standard screw (in this study called “cavity”) there are only small regions with high mixing efficiency which is mainly near the two upper corners of the cavity. If two pins are put into the cavity, large high mixing efficiency regions occur in the scope from cavity top to about 1/3 flight height. But, in the case of inserting two holed pins into the cavity, high mixing efficiency regions are distributed in nearly all over the cavity. It is impossible to get such useful information by experiments. Even though the calculation was confined in cross-section of pin mixing section, it has directive significance in designing the practical pin mixing section in the light of theory of distributive mixing.

Variance and invariants in room acoustics: A random walk through reverberant fields.

The understanding of room reverberation has advanced notably in recent decades owing to the merging of statistical communication theory with room acoustics. New invariants expressed as simple and robust statistical laws govern steady‐state variation of reverberant sound pressure over time, frequency, and space. Much of statistical room acoustics (SRA) theory can be developed by applying random walk theory to classical room acoustics. Reverberation time (T60) controls the variance of reverberant pressure with frequency at each room location. The ‘‘reverberation time‐bandwidth’’ (BT60) product controls spatial variance. SRA contradicts the conventional wisdom that ‘‘hot spots’’ and ‘‘dead spots’’ indicate poor diffusion, implying instead that spatial variations are inevitable even in a perfectly diffuse field. SRA facilitated new measurement standards for estimating pure tone sound power in reverberation rooms by providing objective guidance for optimization of spatial averaging and estimation of error boun...