Strip Region Research Articles

Voltage dependence of effective barrier height reduction in inhomogeneous Schottky diodes

The Schottky barrier height (SBH) variation and its dependence on applied voltage for NiSi/n-Si Schottky diodes with different SBH inhomogeneities have been studied by temperature-dependent current–voltage technique. The results show that the effective barrier height is strongly dependent on the SBH inhomogeneity and the applied voltage. The reduction of effective barrier height increases as the bias varies from forward to reverse, indicating that the pinch off, or more precisely saying, the presence of saddle point in the depletion region, does strongly affect the current transport. Under low reverse bias, the SBH reduction is proportional to one-fourth power of the band bending, which indicates that strip-like SBH inhomogeneity rather than patch-like SBH inhomogeneity exists in our samples. The strip region parameter ω is determined to be 1.63 × 10 −3 and 3.21 × 10 −3 V −1/2 cm −1/2 for the two diodes respectively. Under high reverse bias, the SBH reduction shows different behaviours for diodes with different SBH inhomogeneity. For diodes with small inhomogeneity, the SBH reduction increases faster than the one-fourth power of the band bending while for diodes with large inhomogeneity, the reduction increases more slowly than in the low reverse bias region. The reason is also explained in term of pinch off.

Wavelength-tunable polarization converter utilizing the strain induced by proton exchange in lithium niobate

A new wavelength-tunable polarization converter utilizing the strain induced by proton exchange is demonstrated in x-cut LiNbO3. The light polarization is converted by the strain-optic effect through the phase-matched coupling of two orthogonal polarizations. The stress-applying structure is designed to be composed of several proton-exchanged strip regions for maximization of the stress distribution. The principle of birefringent chain filters is utilized to design the device structure in order to avoid the requirement of large stress, which results in serious cracks on the substrate surface. The overlap integral between the optical field distribution and the stress distribution can be enhanced simply by prolonging the proton-exchange time. Besides, the stress distribution and its strength in the stress-applying structure can be fine tuned without affecting the waveguide characteristics such that the principle of the birefringent chain filters is completely satisfied. Therefore, the polarization-conversion efficiency can be optimized when utilizing this exclusive stress-tuning ability. By the thermal-optic effect, the wavelength of maximum conversion can be tuned at a rate of -0.115 nm/°C with a maximum conversion efficiency of 92.41%. The proposed polarization converter has the advantages of adequate stress distribution and strength, high parameter-tuning feasibility, low propagation loss, easy fabrication, and low fabrication cost.

A deepChandrasurvey of the Groth Strip - I. The X-ray data

We present the results of a 200-ks Chandra observation of part of the Groth Strip region, using the ACIS-I instrument. We present a relatively simple method for the detection of point sources and calculation of limiting sensitivities, which we argue is at least as sensitive and more self-consistent than previous methods presented in the literature. A total of 158 distinct X-ray sources are included in our point-source catalogue in the ACIS-I area. The number counts show a relative dearth of X-ray sources in this region. For example, at a flux limit of 10 -15 erg cm -2 s -1 , around 20 per cent more soft-band sources are detected in the HDF-N and almost 50 per cent more in the ELAIS-N1 field, which we have analysed by the same method for comparison. We find, however, that these differences are consistent with Poisson variations at <2σ significance, and therefore there is no evidence for cosmic variance based on these number counts alone. We determine the average spectra of the objects and find a marked difference between the soft-band-selected sources, which have r = 1.9 typical of unobscured active galactic nuclei (AGN), and the hard-band-selected sources, which have r = 1.0. Reassuringly, the sample as a whole has a mean spectrum of Γ = 1.4 ± 0.1, the same as the X-ray background. None the less, our results imply that the fraction of sources with significant obscuration is only ∼25 per cent, much less than predicted by standard AGN population synthesis models. This is confirmed by direct spectral fitting, with only a handful of objects showing evidence for absorption. After accounting for absorption, all objects are consistent with a mean intrinsic spectrum of r = 1.76 ± 0.08, very similar to local Seyfert galaxies. The survey area is distinguished by having outstanding multiwaveband coverage. Comparison with these observations and detailed discussion of the X-ray source properties will be presented in future papers.

Evolution of a Rippled Membrane during Phospholipase A 2 Hydrolysis Studied by Time-Resolved AFM

The sensitivity of phospholipase A 2 (PLA 2) for lipid membrane curvature is explored by monitoring, through time-resolved atomic force microscopy, the hydrolysis of supported double bilayers in the ripple phase. The ripple phase presents a corrugated morphology. PLA 2 is shown to have higher activity toward the ripple phase compared to the gel phase in 1,2-dimyristoyl -sn-glycero-3-phosphocholine (DMPC) membranes, indicating its preference for this highly curved membrane morphology. Hydrolysis of the stable and metastable ripple structures is monitored for equimolar DMPC/1,2-distearoyl -sn-glycero-3-phosphocholine (DSPC)-supported double bilayers. As shown by high-performance liquid chromatography results, DSPC is resistant to hydrolysis at this temperature, resulting in a more gradual hydrolysis of the surface that leads to a change in membrane morphology without loss of membrane integrity. This is reflected in an increase in ripple spacing, followed by a sudden flattening of the lipid membrane during hydrolysis. Hydrolysis of the ripple phase results in anisotropic holes running parallel to the ripples, suggesting that the ripple phase has strip regions of higher sensitivity to enzymatic attack. Bulk high-performance liquid chromatography measurements indicate that PLA 2 preferentially hydrolyzes DMPC in the DMPC/DSPC ripples. We suggest that this leads to the formation of a flat gel-phase lipid membrane due to enrichment in DSPC. The results point to the ability of PLA 2 for inducing a compositional phase transition in multicomponent membranes through preferential hydrolysis while preserving membrane integrity.

Characteristics of low-dimensional plasmons in a metallic strip monolayer on a semiconductor surface

By means of the time-dependent local-density approximation, we investigate low-dimensional plasmons (LDPL's) in a metallic strip monolayer on a semiconductor surface, namely, LDPL's in a two-dimensional conduction-electron system confined in a strip region. We analyze the energy-loss intensity, the energy dispersion, and the induced-charge distribution of the two plasmon modes at each wave number q along the strip. When the wavelength \ensuremath{\lambda} $(=2\ensuremath{\pi}/q)$ of the mode is considerably smaller than the strip width D, the higher-energy mode (HEM) has a definite character of the area plasmon (APL), and its energy is close to that of the two-dimensional plasmon in an infinite area (pure 2DPL). However, as the mode energy deviates upward from that of the pure 2DPL with an increase in \ensuremath{\lambda}, the induced-charge distribution of the APL evolves into a standing-wave pattern with its free end at the edge. In contrast, the lower-energy mode (LEM) has a definite character of the edge plasmon. When \ensuremath{\lambda} is small compared with D, the induced charge density of the LEM decays slowly on the inside of the strip owing to the influence of the HEM (APL) close to the LEM in energy.

Erratum: XMM‐Newton view of the Hubble Deep Field‐North and Groth‐Westphal Strip regions

AbstractIn the paper, “XMM‐Newton view of the Hubble Deep Field‐North and Groth‐Westphal strip regions” by Miyaji et al. (2003), we found that one of the data points on Fig. 1 was incorrectly plotted. The corrected figure is shown below.

Rapid electrochemical detection and identification of catalase positive micro-organisms

The rapid detection and identification of bacteria has application in a number of fields, e.g. the food industry, environmental monitoring and biomedicine. While in biomedicine the number of organisms present during infection is multiples of millions in the other fields it is the detection of low numbers of organisms that is important, e.g. an infective dose of Escherichia coli O157:H7 from contaminated food is less than 100 organisms. A rapid and sensitive technique has been developed to detect low numbers of the model organism E. coli O55, combining Lateral Flow Immunoassay (LFI) for capture and amperometry for sensitive detection. Nitrocellulose membranes were used as the solid phase for selective capture of the bacteria using antibodies to E. coli O55. Different concentrations of E. coli O55 in Ringers solution were applied to LFI strips and allowed to flow through the membrane to an absorbent pad. The capture region of the LFI strip was placed in close contact with the electrodes of a Clarke cell poised at +0.7 V for the detection of hydrogen peroxide. Earlier research identified that the consumption of hydrogen peroxide by bacterial catalase provided a sensitive indicator of aerobic and facultative anaerobic microorganisms numbers. Modification and application of this technique to the LFI strips demonstrated that the consumption of 8 mM hydrogen peroxide was correlated with the number of microorganisms presented to the LFI strips in the range of 2×10 1–2×10 7 colony forming units (cfu). Capture efficiency was dependent on the number of organisms applied and varied from 71% at 2×10 2 cfu to 25% at 2×10 7 cfu. The procedure was completed in less than 10 min and could detect less than 10 cfu captured from a 200 μl sample applied to the LFI strip. The approached adopted provides proof of principle for the basis of a new technological approach to the rapid, quantitative and sensitive detection of bacteria that express catalase activity.

XMM‐Newton view of the Hubble Deep Field‐North and Groth‐Westphal strip regions

AbstractWe report the progress on our analysis of two deep XMM observations in the areas of Hubble Deep Field‐North and the Groth‐Westphal Strip field. We present the source detection method, Monte‐Carlo simulation on source detection, and our preliminary Log N – Log S relations. Comparing these two fields and other fields in literature, we find up to ∼30% variations in number counts near our flux limits, which are most likely to be due to cosmic variance. This serves as a pilot study for a more systematic investigation. The nature of the X‐ray sources in the Groth‐Westphal field is also discussed in terms of hardness ratios, morphology and spectroscopic properties.

Near optimality of the sinc approximation

Near optimality of the sinc approximation is established in a variety of spaces of functions analytic in a strip region about the real axis, each space being characterized by the decay rate of their elements (functions) in the neighborhood of the infinity.

On the relationship between the δ Scuti and γ Doradus pulsators

We searched for δ Scuti-type pulsations amongst known and candidate γ Doradus stars. The motivations for such a project come from the need to understand the relationship of these two classes of pulsator better, from the present poor knowledge of the hot border of the γ Doradus phenomenon, and from the exciting prospects for asteroseismology should stars be found which have both types of pulsation excited. We acquired 270 h of observations and monitored a total of 26 stars. One target, HD 209295, turned out to be a member of both classes of pulsating star, but this object is peculiar in the sense that it is a close binary. We classify six of our targets as new bona fide γ Doradus stars, whereas nine more are good γ Doradus candidates, and three turned out to be ellipsoidal variables. One of our programme stars was found to be a δ Scuti star, with no additional γ Doradus variations. Furthermore, one star was already known to be a bona fide γ Doradus star, and we could not find an unambiguous explanation for the variability of five more stars. The analysis of our data together with improved knowledge of stars from the literature enabled us to revise the blue border of the γ Doradus phenomenon towards cooler temperatures. This new blue edge is much better defined than the previous one and extends from a temperature of about 7550 K on the ZAMS to 7400 K one magnitude above it. Five bona fide γ Doradus stars we observed are located inside the δ Scuti instability strip, but none of them exhibited observable δ Scuti pulsations. We therefore suggest that γ Doradus stars are less likely to be δ Scuti pulsators compared with other normal stars in the same region of the lower instability strip. In addition, we show that there is a clear separation between the pulsation constants Q of δ Scuti and γ Doradus stars. The γ Doradus stars known to date all have Q>0.23 d.

Numerical Simulation of Geomagnetic Trapping of Anomalous Cosmic Ray Ions

A method for simulating the propagation processes for ions of the anomalous component of cosmic rays in the Earth's magnetic field is described with allowance made for a step-by-step stripping of the ions in the residual atmosphere and their trapping by the geomagnetic field. Numerical results are presented for the geomagnetic trapping of high-energy singly charged oxygen ions penetrating into the stripping region from interplanetary space.

Flow Field Analysis inside a Molten Zn Pot of the Continuous Hot-dip Galvanizing Process.

The flow field inside a molten zinc pot of the continuous hot-dip galvanizing process of steel strips was investigated experimentally. A 1/5-scale transparent water model with induction heaters, scrapers, and baffles was used in this study. Instantaneous velocity fields were measured using a single-frame PIV velocity field measurement technique with varying the strip velocity V s , flow rate Q of the induction heater, scraper location, and baffle type. The general flow pattern inside the strip region is hardly influenced by the strip speed V s , flow rate Q, and the scraper location around the stabilizing roll. When the induction heater is not operated, a pair of vortices is formed in the inner part of the strip: a clockwise rotating flow at the entrance region and a counter-clockwise rotating flow at the exit region. In the exit region outside of the strip, the flow detached from the stabilizing roll divides into two parts: a counter-clockwise rotating flow in the upper region and a clockwise rotating flow in the lower region. For the cases of no scrapper and scrapper, detached from the stabilizing roll, the flow separates from the moving strip and ascends to the free surface. As the flow rate of the induction heater increases, the ascending flow is weakened and the counter-clockwise rotating flow in the upper area of the outside region becomes tranquil. This indicates that the flow in the upper area of the exit region is greatly influenced by the operation of the induction heater. When a scraper is attached onto the stabilizing roll, the separated flow from the strip is guided downward and the up-rising flow around the stabilizing roll becomes slow and tranquil. By attaching baffles near the moving strip in addition to the stabilizing rolls, the flow entrainment into the corner region between the strip and the stabilizing roll is greatly reduced. These flow control devices should be helpful in reducing top drosses in the zinc plating process.

Flow Control Inside a Molten Zn Pot for Improving Surface Quality of Zinc Plated Strips

The flow fields inside a molten Zn pot of continuous hot-chip galvanizing process were investigated experimentally. With varying several parameters including the strip speed Vs, flow rate Q of induction heater. scrapper location and baffle configuration, instantaneous velocity fields were measured using a PIV velocity field measurement technique. Inside the strip region, counter-clockwise rotating flow is dominant. The general flow pattern inside the strip region is nearly not influenced by the strip speed Vs, flow rate Q and the scrapper location. In the exit region, the flow separated from the moving strip due to the existence of a stabilizing roll ascends to the free surface, for the cases of no scrapper and scrapper detached form the roll. On the other hand, the ascending flow to the free surface is decreased, as the flow rate Q of induction heater increases. By installing a baffle around the uprising strip, the flow moving up to the stabilizing roll decreases. In addition, B-type baffle is better than A-type baffle in reducing speed of flow around the stabilizing rolls. However, the flow ascended to the free surface is largely influenced by changing the flow rate Q, and the scrapper location, irrespective of the baffle type.

Microstructure and microtexture of ultrafine ferrite formed in 0.1%C steel using new strip rolling process

A new hot strip rolling process is discussed which is capable of producing ultrafine, equiaxed ferrite grains (i.e. less than 2 µm)in the surface region of steel strip. Both microstructural and texture analysis of low carbon steel strip that has been rolled using this method are used to show that the ferrite forms by strain induced transformation. Analysis by electron backscatter diffraction (EBSD) indicates that a strong ferrite microtexture exists within the individual austenite grains in which the ferrite nucleates. The results from bulk X-ray texture analysis confirm that the ferrite forms as a result of transformation from austenite that has undergone heavy shearing during rolling, with nucleation occurring on the austenite substructure. In the centre region of the strip, a bainitic microstructure forms after rolling during air cooling. In the transition region between the surface and the centre of the strip, ferrite is shown to nucleate to form closely spaced parallel ‘rafts’ of ferrite grains traversing individual austenite grains. Again, EBSD is used to show that the ferrite located within these rafts is strongly textured, which, in combination with microstructural evidence, suggests that this ferrite nucleates along intragranular shear bands that form in the austenite in this region of the strip during rolling.

Boundary integral equations from Hamilton's principle for surface acoustic waves under periodic metal gratings

The procedure describes the derivation of boundary integral equations for surface acoustic waves propagating under periodic metal strip gratings with piezoelectric films. It takes into account the electrical and mechanical perturbations, including the effects of mass loading caused by the gratings with an arbitrary shape. First, an integral equation is derived with line integrals on the boundaries within one period. This derivation is based on Hamilton's principle and uses Lagrange's method of multipliers to alleviate the continuous conditions of the displacement and the electric potential on the boundaries. Second, boundary integral equations corresponding to each substrate, piezoelectric film, metal strip, and free space region are obtained from the integral equation using the Rayleigh-Ritz method for admissible functions. With this procedure, it is not necessary to make any assumptions for separation of the boundary conditions between two neighboring regions. Consequently, we clarify the theoretical basis for the analytical procedure using boundary integral equations for longitudinal LSAW modes.

Sustainable groundwater management of the stressed Coastal aquifer in the Gaza region

This study proposes an empirical approach that can lead to the sustainable management of groundwater resources. This approach enables a comprehensive understanding of an aquifer, delineates distinct hydrological scenarios, and recommends a set of operational activities for each sub-region of the aquifer. The paper focuses on the Coastal aquifer of the Gaza Strip region which has been divided into three sub-regions. The southern sub-region (WSW) is classified as scenario “+a2”, which indicates that it can be used as a multi-annual groundwater reservoir. The northern sub-region (NW-E) is designated scenario “-a2”, where the recommended operational measures include injection of freshwater in wells and cleaning of the surface environment. The third sub-region (CSE), is classified as scenario “-b2”, which requires severe management measures to correct both a negative hydrological and environmental situation. The approach also involves on-going monitoring of the aquifer, and can be considered as an empirical tool to provide preliminary guidelines for long-term groundwater management.

Velocity Field Measurements of Flow inside Snout of Continuous Hot-Dip Galvanizing Process Using a Single-frame PIV Technique.

In the continuous hot-dip galvanizing process of steel strips, the snout has been installed at the entering region of feeding strip into the molten zinc (Zn) pot. However, evaporated Zn particles in the snout cause ash imperfection on the galvanized steel strip surface. In order to resolve this problem, the flow field inside the snout, both on the deoxidization gas flow above the free surface and the molten Zn flow in the Zn pot. has been investigated experientially. For a 1/10 scale water model, flow visualization and PIV (Particle Image Velocimetry) velocity field measurements were carried out at the strip speed V s =1.5 m/s Aluminum flakes (1 μm) and atomized olive oil (3 μm) were used as seeding particles to simulate the molten Zn flow and the deoxidization gas flow, respectively. As a result, the liquid flow in the Zn pot is dominantly influenced by the up-rising flow in diagonal direction caused by the rotating sink roll. For gas flow in front of the strip inside the snout, the large-scale vortex formed by the downward moving strip is dominant. In the rear side of the strip, a counter-clockwise vortex is formed and some of the flow following by the moving strip impinges on the free surface of molten Zn. The liquid flow in front of the strip is governed by the up-rising flow entering the snout, caused by the rotating sink roll. The moving strip affects dominantly the liquid flow behind the strip inside the snout and large amounts of liquid are entrained and followed the moving strip toward the sink roll. A thin boundary layer is formed on the front side due to the up-rising flow, however, a relatively thick boundary layer is formed in the rear side of the strip. Inside the snout, the deoxidization gas flow above the free surface is much faster than the liquid flow in the Zn pot. More ash imperfections are anticipated on the rear surface of the strip where larger influx flow moves toward the strip in the region near the free surface.

Environmental concerns for construction growth in Gaza Strip

The Gaza Strip region is a fragile ecosystem suffering from increasing environmental assaults due to the escalating population growth and the very limited natural resources available to support their development demands. Currently, there are a number of large scale construction projects being implemented in the process of newly developing Palestine. The major challenge in the development context is to maintain ecological balance which is often sacrificed when rapid economical growth is pursued putting enormous pressure on the natural endowments. This implies a search for innovative and new building materials and construction technology in order to minimize the pressure on the environment. The aim of this paper is to study the impact of rapid construction development on the environment in Gaza Strip. It is strongly recommended that Palestine should follow a program to promote sustainable development through the building of better institutions, and providing appropriate information and investment. It is necessary to assess the impacts of the proposed projects in Gaza Strip and to take certain measures to mitigate the negative impacts. There is a need for raising environmental public awareness and training.

Chaotic oscillation of a nonlinear power system

For a nonlinear power transmission system, the residue calculus method is introduced and applied to study its heteroclinic bifurcation. There a cone region and a strip region of parameters are obtained, in which the power transmission system displays chaotic oscillation. This gives a theoretic analysis and a computational method for the purpose to control the nonlinear system with deviation stably running.

Analytical study and numerical experiments for Laplace equation with overspecified boundary conditions

In this paper, the window function, e − αk 2 , is applied to regularize the divergent problem which occurs in the Laplace equation with overspecified boundary conditions in an infinite strip region. To deal with this ill-posed problem, the corner of the L-curve is chosen as the compromise point to determine the optimal α of the Gaussian window, e − αk 2 , so that the high wave-number ( k) content can be suppressed instead of engineering judgement using the concept of a cutoff wave-number. From the examples shown, it is found that a reasonable solution of the unknown boundary potential can be reconstructed, and that both high wave-number content and divergent results can be avoided by using the proposed regularization technique.