A preliminary study on wire sawing and its comparison with the traditional drill and blast method

Abstract. The traditional drill and blast method has been the most common excavation method for excavating underground spaces. It is an effective method in terms of costs and productivity. However, in certain situations, blasting cannot always be used. For example, excavation close to a sensitive area where blasting may cause vibrations must be restricted. Wire saw cutting used together with the drilling and blasting method is an alternative. As wire saw cutting is a relatively new technique for tunnelling, this thesis aims to provide a comprehensive literature review on this method based on previous studies. The purpose of the thesis is to present detailed information and data on the effectiveness and productivity of the wire saw cutting method, the mechanism of saw cutting, the forces of saw cutting and other important parameters related to the use of wire saw cutting. In addition, the theory of blasting vibrations and the effect of pre-cut discontinuity made by wire saw cutting on vibration reduction are discussed. The research also included a site visit and where wire saw cutting together with drilling and blasting were used in tunnel excavation. This study offers extensive knowledge on wire saw cutting and its current state. Based on the literature review and the site visit, the most common advantages and problems of the method are presented. This knowledge can be used in future research to improve the use of wire saw cutting.Tiivistelmä. Perinteisimmin maanalainen louhinta suoritetaan käyttämällä poraus- ja panostusmenetelmää. Menetelmä on tehokas sekä kustannusten että aikataulun osalta. Tietyissä tilanteissa kyseistä louhintamenetelmää ei kuitenkaan pystytä käyttämään perinteiseen tapaan. Tällainen tilanne voi olla esimerkiksi louhinta alueella, jossa räjähdyksen aiheuttamia tärinöitä täytyy rajoittaa lähellä sijaitsevien tärinäherkkien laitteiden tai rakennusten vuoksi. Vaijerisahaus käytettynä yhdessä poraus- ja panostusmenetelmän kanssa on yksi vaihtoehto tärinöiden rajoittamiseksi. Vaijerisahauksen käyttö tunnelikohteissa on suhteellisen uusi louhintamenetelmä. Tästä syystä tämän tutkielman tarkoituksena on tuottaa kattava kirjallisuuskatsaus menetelmän käytöstä. Työssä esitetään tietoa menetelmän tehokkuudesta ja tuottavuudesta, leikkausmekanismiin sekä leikkausvoimiin liittyvää teoriatietoa sekä muuta tärkeää informaatiota menetelmään ja sen käyttöön liittyen. Tämän lisäksi työssä käsitellään räjäytystärinöitä sekä niiden etenemistä kallioperässä. Tämän pohjalta pohditaan vaijerisahauksella leikatun uran vaikutusta räjäytystärinöiden etenemiseen. Työn aikana suoritettiin myös vierailu tunnelityömaalle Ruotsiin, jossa vaijerisahausta käytettiin poraus- ja panostusmenetelmän apuna räjäytystärinöiden vähentämiseksi. Työn tavoitteena on tarjota laaja katsaus vaijerisahaukseen ja sen nykyiseen tilaan kalliorakentamisen kohteissa kirjallisuuden ja työmaavierailun pohjalta. Tulevissa tutkimuksissa tätä tietoa voidaan hyödyntää kyseisen louhintamenetelmän kehittämiseen

The Structure of the [Zn_In - V_P] Defect Complex in Zn Doped InP

We study the structure, the formation and binding energies and the transfer levels of the zinc-phosphorus vacancy complex [Zn_In - V_P] in Zn doped p-type InP, as a function of the charge, using plane wave ab initio DFT-LDA calculations in a 64 atom supercell. We find a binding energy of 0.39 eV for the complex, which is neutral in p-type material, the 0/-1 transfer level lying 0.50 eV above the valence band edge, all in agreement with recent positron annihilation experiments. This indicates that, whilst the formation of phosphorus vacancies (V_P) may be involved in carrier compensation in heavily Zn doped material, the formation of Zn-vacancy complexes is not. Regarding the structure: for charge states Q=+6 to -4 the Zn atom is in an sp^2 bonded DX position and electrons added/removed go to/come from the remaining dangling bonds on the triangle of In atoms. This reduces the effective vacancy volume monatonically as electrons are added to the complex, also in agreement with experiment. The reduction occurs through a combination of increased In-In bonding and increased Zn-In electrostatic attraction. In addition, for certain charge states we find complex Jahn-Teller behaviour in which up to three different structures, (with the In triangle dimerised, antidimerised or symmetric) are stable and are close to degenerate. We are able to predict and successfully explain the structural behaviour of this complex using a simple tight binding model.Comment: 10 pages text (postscript) plus 8 figures (jpeg). Submitted to Phys. Rev.

First-principles study of He in Si

We have performed first-principles calculations for He atoms in a Si lattice. From dynamic total-energy minimization we obtain the relaxations of the Si atoms around the impurity and the corresponding total energies. The calculated heat of solution and the diffusion constant of He in Si are in good agreement with experiment. There is a net attraction between two tetrahedral He interstitials, leading to a binding energy of 0.08 eV for He atoms at neighboring interstices. On the other hand, Si vacancies are found not to trap He atoms. The consequences of these results to He-bubble nucleation and growth are discussed.Peer reviewe

Short-term herbivory has long-term consequences in warmed and ambient high Arctic tundra

Source at https://doi.org/10.1088/1748-9326/aa579d. Climate change is occurring across the world, with effects varying by ecosystem and region but already occurring quickly in high-latitude and high-altitude regions. Biotic interactions are important in determining ecosystem response to such changes, but few studies have been long- term in nature, especially in the High Arctic. Mesic tundra plots on Svalbard, Norway, were subjected to grazing at two different intensities by captive Barnacle geese from 2003–2005, in a factorial design with warming by Open Top Chambers. Warming manipulations were continued through 2014, when we measured vegetation structure and composition as well as growth and reproduction of three dominant species in the mesic meadow. Significantly more dead vascular plant material was found in warmed compared to ambient plots, regardless of grazing history, but in contrast to many short-term experiments no difference in the amount of living material was found. This has strong implications for nutrient and carbon cycling and could feed back into community productivity. Dominant species showed increased flowering in warmed plots, especially in those plots where grazing had been applied. However, this added sexual reproduction did not translate to substantial shifts in vegetative cover. Forbs and rushes increased slightly in warmed plots regardless of grazing, while the dominant shrub, Salix polaris , generally declined with effects dependent on grazing, and the evergreen shrub Dryas octopetala declined with previous intensive grazing . There were no treatment effects on community diversity or evenness. Thus despite no changes in total live abundance, a typical short-term response to environmental conditions, we found pronounced changes in dead biomass indicating that tundra ecosystem processes respond to medium- to long-term changes in conditions caused by 12 seasons of summer warming. We suggest that while high arctic tundra plant communities are fairly resistant to current levels of climate warming, underlying ecosystem processes are beginning to change. In addition, even short bouts of intense herbivory can have long-term consequences for some species in these communities

MVG Mechanism: Differential Privacy under Matrix-Valued Query

Differential privacy mechanism design has traditionally been tailored for a scalar-valued query function. Although many mechanisms such as the Laplace and Gaussian mechanisms can be extended to a matrix-valued query function by adding i.i.d. noise to each element of the matrix, this method is often suboptimal as it forfeits an opportunity to exploit the structural characteristics typically associated with matrix analysis. To address this challenge, we propose a novel differential privacy mechanism called the Matrix-Variate Gaussian (MVG) mechanism, which adds a matrix-valued noise drawn from a matrix-variate Gaussian distribution, and we rigorously prove that the MVG mechanism preserves $(\epsilon,\delta)$-differential privacy. Furthermore, we introduce the concept of directional noise made possible by the design of the MVG mechanism. Directional noise allows the impact of the noise on the utility of the matrix-valued query function to be moderated. Finally, we experimentally demonstrate the performance of our mechanism using three matrix-valued queries on three privacy-sensitive datasets. We find that the MVG mechanism notably outperforms four previous state-of-the-art approaches, and provides comparable utility to the non-private baseline.Comment: Appeared in CCS'1

Metastable defect complexes in GaAs

We have studied the As-vacancy–Si-impurity and the As-vacancy–As-antisite complexes in GaAs using state-of-the-art electronic structure methods. The complexes show metastability as a function of the position of the impurity or the antisite atom similarly to the large-lattice relaxation models for the isolated DX and EL2 centers. Our findings suggest the enlargement of the family of metastable defects in GaAs, and the results enlighten the metastability mechanisms in the large-lattice relaxation model. In order to discuss the possible experimental detection of this type of metastability, we calculate the positron states and annihilation characteristics for the defect complexes.Peer reviewe

Shocked POststarbust Galaxy Survey I: Candidate Poststarbust Galaxies with Emission Line Ratios Consistent with Shocks

[Abridged] The Shocked POststarburst Galaxy Survey (SPOGS) aims to identify transforming galaxies, in which the nebular lines are excited via shocks instead of through star formation processes. Utilizing the OSSY measurements on the Sloan Digital Sky Survey Data Release 7 catalog, we applied Balmer absorption and shock boundary criteria to identify 1,067 SPOG candidates (SPOGs*) within z=0.2. SPOGs* represent 0.2% of the OSSY sample galaxies that exceed the continuum signal-to-noise cut (and 0.7% of the emission line galaxy sample). SPOGs* colors suggest that they are in an earlier phase of transition than OSSY galaxies that meet an E+A selection. SPOGs* have a 13% 1.4GHz detection rate from the Faint Images of the Radio Sky at Twenty centimeters survey, higher than most other subsamples, and comparable only to low-ionization nuclear emission line region hosts, suggestive of the presence of active galactic nuclei. SPOGs* also have stronger NaD absorption than predicted from the stellar population, suggestive of cool gas being driven out in galactic winds. It appears that SPOGs* represent an earlier phase in galaxy transformation than traditionally selected poststarburst galaxies, and that a large proportion of SPOGs* also have properties consistent with disruption of their interstellar media, a key component to galaxy transformation. It is likely that many of the known pathways to transformation undergo a SPOG phase. Studying this sample of SPOGs* further, including their morphologies, active galactic nuclei properties, and environments, has the potential for us to build a more complete picture of the initial conditions that can lead to a galaxy evolving.Comment: 19 pages, 19 figures, 3 tables, accepted to ApJ Supplements (Apr 13), full sample is available on www.spogs.or

Lingering Chukchi Sea sea ice and Chukchi Sea mean winds influence population age structure of euphausiids (krill) found in the bowhead whale feeding hotspot near Pt. Barrow, Alaska

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ashjian, C. J., Okkonen, S. R., Campbell, R. G., & Alatalo, P. Lingering Chukchi Sea sea ice and Chukchi Sea mean winds influence population age structure of euphausiids (krill) found in the bowhead whale feeding hotspot near Pt. Barrow, Alaska. Plos One, 16(7), (2021): e0254418, https://doi.org/10.1371/journal.pone.0254418.Interannual variability in euphausiid (krill) abundance and population structure and associations of those measures with environmental drivers were investigated in an 11-year study conducted in late August–early September 2005–2015 in offshelf waters (bottom depth > 40 m) in Barrow Canyon and the Beaufort Sea just downstream of Distributed Biological Observatory site 5 (DBO5) near Pt. Barrow, Alaska. Statistically-significant positive correlations were observed among krill population structure (proportion of juveniles and adults), the volume of Late Season Melt Water (LMW), and late-spring Chukchi Sea sea ice extent. High proportions of juvenile and adult krill were seen in years with larger volumes of LMW and greater spring sea ice extents (2006, 2009, 2012–2014) while the converse, high proportions of furcilia, were seen in years with smaller volumes of LMW and lower spring sea ice extent (2005, 2007, 2010, 2011, 2015). These different life stage, sea ice and water mass regimes represent integrated advective responses to mean fall and/or spring Chukchi Sea winds, driven by prevailing atmospheric pressure distributions in the two sets of years. In years with high proportions of juveniles and adults, late-spring and preceding-fall winds were weak and variable while in years with high proportions of furcilia, late-spring and preceding-fall winds were strong, easterly and consistent. The interaction of krill life history with yearly differences in the northward transports of krill and water masses along with sea ice retreat determines the population structure of late-summer krill populations in the DBO5 region near Pt. Barrow. Years with higher proportions of mature krill may provide larger prey to the Pt. Barrow area bowhead whale prey hotspot. The characteristics of prey near Pt. Barrow is dependent on krill abundance and size, large-scale environmental forcing, and interannual variability in recruitment success of krill in the Bering Sea.This research was supported by the National Science Foundation through grants PLR-1023331 (CJA), OPP-0436131 (CJA), PLR-1022139 (RGC), OPP-0436110 (RGC), PLR-1023446 (SRO), and OPP-043166 (SRO), the National Oceanic and Atmospheric Administration (NOAA) under cooperative agreement NA08OAR4320751 with the University of Alaska (SRO) and cooperative agreements NA17RJ1223 and NA09OAR4320129 with the Woods Hole Oceanographic Institution (CJA), the Bureau of Ocean Energy Management through Interagency Agreement 0106RU39923/M08PG20021 between the National Marine Fisheries Service and MMS/BOEM (CJA, RGC, SRO) and through the National Oceanographic Partnership Program award number N00014-08-1-0311 from the Office of Naval Research to the Woods Hole Oceanographic Institution (CJA, SRO, RGC). Additional support was provided by the Coastal Marine Institute at the University of Alaska (SRO, RGC) and the James M. and Ruth P. Clark Arctic Research Initiative Fund at the Woods Hole Oceanographic Institution (CJA). The participation of the K-12 teachers was supported by the National Science Foundation through the ARMADA program at the University of Rhode Island (2005, 2006) and through the POLARTrec program at the Arctic Research Consortium of the United States (2012)