Ambiguous Correlation Research Articles

An allostratigraphic approach to subdivide fine-grained sediments for urban planning

Fine-grained sediments in southern Finland were deposited during the retreat of the continental Fennoscandian ice-sheet at around 13,000 cal BP, leaving subsequent ice-contact deposits and postglacial lake and, finally, the modern brackish water Baltic Sea basin (BSB). As a result of the strong glacioisostatic land uplift of the region, these sediments today lie above sea-level in coastal Finland. The recent expansion of cities to locations where superficial sediments are more challenging for construction purposes has increased the need for comprehensive understanding of the properties and geometry of these fine-grained superficial deposits. Commonly used site-specific lithostratigraphical characteristics of clayey deposits run the risk of ambiguous correlation between sites because of different types of postglacial depositional settings. The present study applies an allostratigraphical approach to classify late- and postglacial clayey deposits using examples from four sedimentary basins in the vicinity of the city of Espoo along the southern coast of Finland. This entails a reinterpretation of 17 core logs collected during the period 2006–2009 and reported in earlier studies, combined with examination of five new cores collected in 2016 coupled with borehole measurements of resistivity-temperature and electrical resistivity tomography (ERT). Physical proxies and sediment characteristics demonstrate that grey postglacial lacustrine silty (Ancylus Lake) clay is truncated at the top by an undulating erosional surface (unconformity), which is covered by a silt to sand layer a few centimetres thick that has a gradual-bioturbated upper contact to the greenish-grey brackish water (Litorina Sea) mud. Sediments above and below the unconformity are intensely bioturbated, and black mottling of Fe-monosulphide is observed in the brackish water mud. Evidently, this unconformity is of high engineering-geological significance because the organic-rich brackish water mud has a poorer bearing capacity and higher abundance of sulphide minerals that form sulphuric acid upon oxidation. It is demonstrated that this unconformity is spatially well recognised and provides a key stratigraphic marker for wider and more accurate comparison between sites with fine-grained deposits in the Helsinki metropolitan area and potentially in other urban areas in the northern Baltic Sea region.

Photometric and spectroscopic study of the supergiant with an infrared excess V1027 Cygni

We present the results of our $UBV$ and $JHKLM$-photometry for the semiregular pulsating variable V1027~Cyg, a supergiant with an infrared excess, over the period from 1991 to 2015. Our search for a periodicity in the $UBV$ brightness variations has led to several periods from $P=212^{d}$ to $P=320^{d}$ in different time intervals. We have found the period $P=237^{d}$ based on our infrared photometry. The variability amplitude, the light-curve shape, and the magnitude of V1027~Cyg at maximum light change noticeably from cycle to cycle. An ambiguous correlation of the $B-V$ and $U-B$ colors with the brightness has been revealed. The spectral energy distribution for V1027~Cyg from our photometry in the range 0.36 ($U$)-5.0 ($M$) $\mu$m corresponds to spectral types from G8I to K3I at different phases of the pulsation cycle. Low-resolution spectra of V1027 Cyg in the range $\lambda$4400--9200 \AA\ were taken during 16 nights over the period 1995--2015. At the 1995 and 2011 photometric minima the star's spectrum exhibited molecular TiO bands whose intensity corresponded to spectral types M0--M1, while the photometric data point to a considerably earlier spectral type. We hypothesize that the TiO bands are formed in the upper layers of the extended stellar atmosphere. We have measured the equivalent widths of the strongest absorption lines, in particular, the infrared Ca~II triplet in the spectrum of V1027~Cyg. The calcium triplet (Ca T) with $W_{\lambda}(\mathrm{Ca~T})=20.3\pm1.8$ \AA\ as a luminosity indicator for supergiants places V1027 Cyg in the region of the brightest G--K supergiants. V1027 Cyg has been identified with the infrared source IRAS~20004+2955 and is currently believed to be a candidate for post-AGB stars. The evolutionary status of the star and its difference from other post-AGB objects are discussed.

Non-zero-sum reinsurance games subject to ambiguous correlations

This paper studies the economic implications of ambiguous correlation in a non-zero-sum game between two insurers. We establish the general framework of Nash equilibrium for the coupled optimization problems. For the constant absolute risk aversion (CARA) insurers, we show that the equilibrium reinsurance strategies admit closed-form solutions. Our results indicate that the ambiguous correlation leads to an increase in the equilibrium demand of reinsurance protection for both insurers. Numerical studies examine the effect on the quality of the correlation estimations.

Portfolio Optimization with Ambiguous Correlation and Stochastic Volatilities

In a continuous-time economy, we investigate the asset allocation problem among a risk-free asset and two risky assets with an ambiguous correlation between the two risky assets. The portfolio selection that is robust to the uncertain correlation is formulated as the utility maximization problem over the worst-case scenario with respect to the possible choice of correlation. Thus, it becomes a maximin problem. We solve the problem under the Black--Scholes model for risky assets with an ambiguous correlation using the theory of $G$-Brownian motions. We then extend the problem to stochastic volatility models for risky assets with an ambiguous correlation between risky asset returns. An asymptotic closed-form solution is derived for a general class of utility functions, including constant relative risk aversion and constant absolute risk aversion utilities, when stochastic volatilities are fast mean reverting. We propose a practical trading strategy that combines information from the option implied volatility surfaces of risky assets through the ambiguous correlation.

Non-zero-sum Reinsurance Games Subject to Ambiguous Correlations

This paper studies the economic implications of ambiguous correlation in a non-zero-sum game between two insurers. We establish the general framework of Nash equilibrium for the coupled optimization problems. For the constant absolute risk aversion (CARA) insurers, we show that the equilibrium reinsurance strategies admit closed-form solutions. Our results indicate that the ambiguous correlation leads to an increase in the equilibrium demand of reinsurance protection for both insurers. Numerical studies examine the effect on the quality of the correlation estimations.

AUV Underwater Positioning Algorithm Based on Interactive Assistance of SINS and LBL.

This paper studies an underwater positioning algorithm based on the interactive assistance of a strapdown inertial navigation system (SINS) and LBL, and this algorithm mainly includes an optimal correlation algorithm with aided tracking of an SINS/Doppler velocity log (DVL)/magnetic compass pilot (MCP), a three-dimensional TDOA positioning algorithm of Taylor series expansion and a multi-sensor information fusion algorithm. The final simulation results show that compared to traditional underwater positioning algorithms, this scheme can not only directly correct accumulative errors caused by a dead reckoning algorithm, but also solves the problem of ambiguous correlation peaks caused by multipath transmission of underwater acoustic signals. The proposed method can calibrate the accumulative error of the AUV position more directly and effectively, which prolongs the underwater operating duration of the AUV.

Fibrous TiO2 gas sensors produced by electrospinning

Gas sensors produced by electrospinning demonstrate high performance in terms of sensitivity, reversibility, response and recovery time. These merits were attributed to their nanostructured fibrous morphology with high surface area and small grain size. This hypothesis is examined in this work by comparing the gas sensing properties of fibrous TiO2 gas sensors obtained by electrospinning. Sensors with markedly different grain size and specific surface area, obtained by changing process parameters such as the polymer solution (PVAc or PMMA) and calcination temperature (450 or 750 °C) displayed rather ambiguous correlation between the morphology and gas sensitivity. The sensors that were calcined at 750 °C were found to be more sensitive than their 450 °C calcined counterparts, for the most part, despite having larger grain size and smaller specific surface area. This unexpected result questions the dogma regarding the correlation between sensor morphology and gas sensitivity, suggesting that another effect might be at play.

Ambiguous correlation of precisely dated coral detritus with the tsunamis of 1861 and 1907 at Simeulue Island, Aceh Province, Indonesia

Precise U-Th dates from coral detritus in two pre-2004 tsunami deposits on Simeulue Island in Aceh Province allow us to correlate the deposits with historically documented tsunamis in the recent few centuries, but because of potential discordance between the death dates of the corals and deposition of the sand layers, ambiguity in this correlation remains. Pits at coastal lowland sites exposed sand layers beneath the 2004 tsunami deposit at Busung and Naibos on southern Simeulue Island. The layers share sedimentological characteristics with the deposit of the 2004 tsunami, and are interpreted as pre-2004 tsunami deposits. Historical accounts document earthquakes and tsunamis in 1907 and 1861 and suggest that the 1907 tsunami was larger locally than any others historically. Nonetheless, U-Th analyses of coral boulders in the younger of two pre-2004 deposits at Busung and in the lone deposit at Naibos yielded dates of death that overlap with 1861, but there were no tsunami layers that could be directly dated to 1907. The younger pre-2004 sand deposit can be attributed to both the 1861 and 1907 events, if the dated corals were killed by uplift in 1861 and subsequently entrained and deposited by the 1907 tsunami. A piece of coral in the older of the two pre-2004 sand layers at Busung dated to around AD 1783, and was deposited by an unknown tsunami that occurred after AD 1783, or possibly by the 1861 tsunami. The nearly equatorial latitude of the study sites minimizes potential for geological confusion between tsunami and storm. Our results show the difficulty in matching known events and geological records when using limiting maximum ages from allochthonous fossils, even with high precision radiometric dates.

Portfolio Optimization with Ambiguous Correlation and Stochastic Volatilities

In a continuous-time economy, we investigate the asset allocation problem among a risk-free asset and two risky assets with an ambiguous correlation between the two risky assets. The portfolio selection that is robust to the uncertain correlation is formulated as the utility maximization problem over the worst-case scenario with respect to the possible choice of correlation. Thus, it becomes a maximin problem. We solve the problem under the Black-Scholes model for risky assets with an ambiguous correlation using the theory of G-Brownian motions. We then extend the problem to stochastic volatility models for risky assets with an ambiguous correlation between risky asset returns. An asymptotic closed-form solution is derived for a general class of utility functions, including CRRA and CARA utilities, when stochastic volatilities are fast mean-reverting. We propose a practical trading strategy that combines information from the option implied volatility surfaces of risky assets through the ambiguous correlation.

Proposed reassessment of the Cambrian GSSP

Since the time of its ratification in 1992, the Cambrian GSSP, 2.3m above the base of Member 2A (Quaco Road Member) of the Chapel Island Formation, Fortune Head section, Newfoundland, Canada, has been challenged as posing an ambiguous correlation level. Difficulties have been encountered in precisely correlating the horizon coinciding with the GSSP to strata on most paleocontinents, but especially to Siberia and South China (Gondwana). The GSSP point, which was intended to coincide with the base of the Treptichnus pedum (formerly Phycodes pedum or Trichophycus pedum) Ichnozone at the FAD of the trace fossil T. pedum, occurs above the first appearance of the trace in the stratotype section. Trace fossils of other forms in the stratotype provide a means of bracketing the position of the GSSP, but are imprecise guides for correlation globally. Other chronostratigraphic guides are unavailable at the stratotype because of a dominance of coarse siliciclastic lithologies and metamorphic overprint.To facilitate global correlation of the Cambrian base and ensure nomenclatural stability to the extent possible, discussion of the merits and perceived weaknesses of the Cambrian GSSP is sought. Possible solutions to the problems surrounding the current GSSP definition are addressed in hopes that the global scientific community will actively participate in developing a well-reasoned, practical solution that will stand the test of time.

THE LUNAR THERMAL ICE PUMP

It has long been suggested that water ice can exist in extremely cold regions near the lunar poles, where sublimation loss is negligible. The geographic distribution of H-bearing regolith shows only a partial or ambiguous correlation with permanently shadowed areas, thus suggesting that another mechanism may contribute to locally enhancing water concentrations. We show that under suitable conditions, water molecules can be pumped down into the regolith by day-night temperature cycles, leading to an enrichment of H2O in excess of the surface concentration. Ideal conditions for pumping are estimated and found to occur where the mean surface temperature is below 105 K and the peak surface temperature is above 120 K. These conditions complement those of the classical cold traps that are roughly defined by peak temperatures lower than 120 K. On the present-day Moon, an estimated 0.8% of the global surface area experiences such temperature variations. Typically, pumping occurs on pole-facing slopes in small areas, but within a few degrees of each pole the equator-facing slopes are preferred. Although pumping of water molecules is expected over cumulatively large areas, the absolute yield of this pump is low; at best, a few percent of the H2O delivered to the surface could have accumulated in the near-surface layer in this way. The amount of ice increases with vapor diffusivity and is thus higher in the regolith with large pore spaces.

Returns to specialization, competition, population, and growth

Using an expanding-variety endogenous growth model with purposive human capital accumulation, this paper provides an alternative explanation of why we may observe an ambiguous correlation between product market competition (PMC) and economic growth, and between population and economic growth rates. Our explanation is based on the notion of ‘returns to specialization’. Under the model's assumptions, PMC and economic growth are ambiguously correlated when returns to specialization are decreasing, whereas population growth and productivity growth are ambiguously correlated when returns to specialization are increasing. From a theoretical point of view, these results are explained by the presence or absence of an ‘increasing production-complexity’ effect associated to the use of a larger number of intermediate-input varieties in the same production process.

Quantitative carbon ion beam radiography and tomography with a flat-panel detector

High dose gradients are inherent to ion beam therapy. This results in high sensitivity to discrepancies between planned and delivered dose distributions. Therefore an accurate knowledge of the ion stopping power of the traversed tissue is critical. One proposed method to ensure high quality dose deposition is to measure the stopping power by ion radiography. Although the idea of imaging with highly energetic ions is more than forty years old, there is a lack of simple detectors suitable for this purpose. In this study the performance of an amorphous silicon flat-panel detector, originally designed for photon imaging, was investigated for quantitative carbon ion radiography and tomography. The flat-panel detector was exploited to measure the water equivalent thickness (WET) and water equivalent path length (WEPL) of a phantom at the Heidelberg Ion–Beam Therapy Center (HIT). To do so, the ambiguous correlation of detector signal to particle energy was overcome by active or passive variation of carbon ion beam energy and measurement of the signal-to-beam energy correlation. The active method enables one to determine the WET of the imaged object with an uncertainty of 0.5 mm WET. For tomographic WEPL measurements the passive method was exploited resulting in an accuracy of 0.01 WEPL. The developed imaging technique presents a method to measure the two-dimensional maps of WET and WEPL of phantoms with a simple and commercially available detector. High spatial resolution of 0.8 × 0.8 mm2 is given by the detector design. In the future this powerful tool will be used to evaluate the performance of the treatment planning algorithm by studying WET uncertainties.

Favorable conditions for energetic electron acceleration during magnetic reconnection in the Earth's magnetotail

[1] We have studied favorable conditions for energetic electron acceleration during magnetic reconnection in the Earth's magnetosphere using the Geotail data. We have found the strong energetic electron acceleration in some reconnection events. On the other hand, the other reconnection events show weak electron acceleration. To discuss what reconnection characteristics determine energetic electron acceleration efficiency, we have studied the reconnection characteristics for 10 events in which the Geotail satellite observed the vicinity of the diffusion region. We have classified the relationship between the reconnection characteristics and the electron acceleration efficiency into three types: (1) good correlation (absolute value of correlation coefficient ∣r∣ > 0.6); (2) ambiguous correlation (0.6 > ∣r∣ > 0.3); and (3) no correlation (0.3 > ∣r∣). We found that ion heating, electron heating, current sheet thickness, reconnection electric field, and converging normal electric field could be categorized into good correlation. Ion/electron temperature ratio, total amount of reconnected magnetic energy, and reconnection rate were classified in ambiguous correlation. We could not find any correlation between energetic electron acceleration efficiency and absolute value of outflow velocity, current density parallel to magnetic field (Hall current system), and satellite location in the Earth's magnetosphere. From our analysis we claimed that the electrons are efficiently accelerated in a thin current sheet during fast reconnection events.

Application of a novel nonperiodic grating in scanning probe microscopy drift measurement

A technique based on two-dimensional nonperiodic grating is proposed to quantitatively measure the drift of scanning probe microscopy (SPM) instruments. Cross-correlation image analysis is adopted in determining the drift. The grating, named as zero-reference mark (ZRM), has specially designed codes and arrangement of the elements can be optimized to have maximum ratio of maximum peak to second maximum of the image correlation matrix. Design considerations of ZRM for drift measurement are discussed theoretically. Advantages of applying ZRM are analyzed by numerical simulation. Comparisons between ZRM and periodic grating show that ZRM has a sharper, less ambiguous correlation function. Adopting ZRM is much more insensitive to drift larger than one element width. Measurement sensitivity is improved by almost one order of magnitude. These characteristics of ZRM imply that it is suitable to be severed as a reference mark for SPM drift measurement.

Surface Chemical Characteristics of CMP Polyurethane Pads

ABSTRACTAttenuated total reflection FT-IR spectroscopy coupled with a hydrogen-deuterium exchange technique is employed to investigate the surface chemistry of two polishing pads, a thermoplastic polyurethane (TPU) pad and a commercial cast urethane (PU) pad. A time/temperature-dependent reduction of nitrogen-hydrogen stretching modes (νN-H) was observed when the pads were immersed in deuterium oxide (D2O). Compared to TPU pads, the PU pads showed an ambiguous correlation between dependence of the band intensity changes and D2O-immersion time/temperature. For both types of pads, a sharp decrease in νN-H band intensity and an unexpected rebound in νN-H band intensity were observed within 24 hrs after immersing the pads in D2O. However, a comparable rebound in νN-H band intensity was not observed for conditioned TPU pad samples. This phenomenon is proposed to be due to a rearrangement of polar groups at the pad surface when the pad is immersed in water, which may influence pad performance on the asperity level.

Revisiting the B-factor variation in a-SiC:H deposited by HWCVD

In order to understand material properties in a better way, it is always desirable to come up with new variables that might be related to the film properties. The B-parameter is such a variable, which relates to the quality of a-SiC:H films both in terms of electronic and optical properties. B (scaling factor) is essentially the slope of the straight-line part of the (α E) 1/2– E (Tauc plot). Due to dependence on a large number of parameters and no detailed research, many previous authors have surmised that B has an ambiguous correlation with carbon content. We have made an attempt to establish the relation between the B-parameter as a quality-indicating factor of a-SiC:H films in both carbon- and silicon-rich material. For this we studied a-SiC:H films deposited by the HWCVD method with broad deposition parameters of substrate temperature ( T s), filament temperature ( T F) and C 2H 2 fraction. Our results indicate that the B-parameter varies considerably with process conditions such as T F, total gas pressure and carbon content. An attempt is made to correlate the B-parameter with an opto-electronic parameter, such as the mobility edge, which has relevance to the device-quality aspects of a-SiC:H films prepared by HWCVD.

Flavonóides das flores de Stiffitia chrysantha Mikan

The flowers of Stiffitia chrysantha Mikam(Asteraceae) contain eriodictiol, quercetin, luteolin and b-D-glycopyranosil-sitosterol. These compounds and its derivatives were identified by their 1H and 13C NMR, infra-red and mass spectra data. The heteronuclear 2D NMR were used to confirm the assignments of the proton and carbon chemical shifts, it was used to eliminate definitively the ambiguous correlation reported in the literature for C-5 and C-9 of quercetin and C-23 and C-25 of b-D-glycopyranosil-sitosterol.

Magnetic susceptibility patterns in a Cordilleran granitoid: The Las Tazas Complex, northern Chile

The Las Tazas Complex is a ferromagnetic I‐type granitoid that crops out in the Coastal Cordillera of northern Chile. Magnetic susceptibility patterns across the complex are controlled by modal magnetite contents, rather than overall mineralogy, resulting in an ambiguous correlation between susceptibility magnitude variation and lithological zoning. There is a good correlation between plagioclase magmatic fabric orientations and magnetic fabric orientation, demonstrating that anisotropy of magnetic susceptibility (AMS) measurements can accurately characterize magmatic fabric patterns in Cordilleran I‐type granitoids. However, there is no simple quantitative relationship between magmatic and magnetic fabric intensities. The magmatic and magnetic fabrics share a similar character, and it is clear that AMS fabrics are strongly influenced by the dominant plagioclase fabric across the Las Tazas Complex but cannot be directly equated in quantitative strain analysis.

Lack of correlation between site of wrist pain and location of noncommunicating defects shown by three-compartment wrist arthrography.

Communicating defects shown by wrist arthrography often correlate poorly with the location of the patient's symptom(s). No study of wrist arthrography in which noncommunicating defects have been isolated, described, and correlated with the site of patients' symptoms has been reported. The aim of this study was to correlate the site(s) of patients' pain and the location(s) of noncommunicating defects shown by wrist arthrography. One hundred noncommunicating capsular defects and incomplete defects of the interosseous ligaments and triangular fibrocartilage in 82 patients were identified from 462 three-compartment wrist arthrograms. Correlation between the sites of pain and sites of the noncommunicating defect was described as: (1) exact correlation, (2) ulnar/radial side correlation, (3) ambiguous correlation, or (4) no correlation. Statistical analysis was performed for each type of defect separately, in aggregate for patients who had more than one defect, and by separate analysis using patients' age (less than or greater than 30 years old). Capsular defects were detected in 65 patients, incomplete perforations of the triangular fibrocartilage in 28 patients, and incomplete defects of the scapholunate and lunotriquetral ligament in three patients each. No statistically significant correlation was found between individual defects and symptoms or between the site(s) of symptoms and patterns of multiple noncommunicating defects. Further, age did not influence the degree of correlations (chi 2 = 0.000-0.476, p values = 0.49-1.00). Attribution of patient's symptoms to noncommunicating defects shown by wrist arthrography is not reliable. Cases in which site-specific arthrographic defects directly correlate may be fortuitous. Additional studies will be necessary to determine the future role of wrist arthrography in the evaluation of the painful wrist.