Tunnel Type Research Articles

Eficacia de secador solar tipo túnel con cacao (Theobroma Cacao L.) en Tabasco

El secado de cacao en la región de la Chontalpa, Tabasco, México realizado por los campesinos se realiza principalmente al aire libre en patio de cemento o bien, en secadores construidos con madera. Con este tipo de secado puede haber contaminación con polvo, hongos y animales que afectan la inocuidad del grano seco. Las beneficiadoras de la región emplean gas como insumo para el secado artificial, lo cual incrementa el costo y la huella ecológica de producto obtenido. Durante la temporada seca el proceso de secado requiere hasta 3.5 días y en temporada de lluvias pocos productores la llevan a cabo. El presente trabajo tuvo como objetivo conocer la eficacia del tiempo de secado de grano de cacao con un secador solar tipo túnel de policarbonato, durante el periodo canicular y la satisfacción por parte del productor participante, en la región de la Chontalpa, Tabasco. Se realizó una prueba en agosto de 2017, con medición de las variables atmosféricas: temperatura y humedad relativa, en una finca ubicada entre las coordenadas 18° 0’ 36’’ latitud norte y 93° 18’ 18’’ longitud oeste. Los resultados obtenidos indican que en 24 h se logra cumplir con el porcentaje de humedad en el grano requerido por la norma NMX-F-352-S-1980 y la satisfacción del productor participante relacionada con las características de color interno y externo, olor, sonido, peso final, separación de la cascarilla y presencia de hongos del grano seco de cacao.

Synthesis, Crystal Structure and Properties of a New Phosphate, Na2Co2Cr(PO4)3

In this work, a novel phosphate Na2Co2Cr(PO4)3 was synthesized by sol–gel method, and its crystal structure was determined from powder X-ray diffraction data using Rietveld method. This new phosphate was further characterized by scanning electron microscopy, IR and Raman spectroscopy. This phosphate crystallizes in the well-known alluaudite-type structure with monoclinc symmetry (S.G. C 2/c). The structure of this phosphate consists of [CoO6] octahedra, [(Co,Cr)2O10] dimer-octahedra and PO4 tetrahedra leading to an open three-dimensional framework containing two types of tunnels running along [001] direction, where Na+ cations are located. The magnetic measurements confirmed that the predominant interactions in this phosphate are antiferromagnetic with a Curie–Weiss constant of θ = − 4.57 K. The electrochemical properties of Na2Co2Cr(PO4)3 as anode material for sodium-ion batteries were assessed using a galvanostatic mode and cyclic voltammetry in the potential window of 0.02–3 V. The electrochemical behavior was investigated by ex situ X-ray diffraction. The results showed that this material undergoes a conversion-type reaction.

Symmetry breaking and unconventional charge ordering in single crystal Na2.7Ru4O9

The interplay of charge, spin, and lattice degrees of freedom in matter leads to various forms of ordered states through phase transitions. An important subclass of these phenomena of complex materials is charge ordering (CO), mainly driven by mixed-valence states. We discovered by combining the results of electrical resistivity ($\rho$), specific heat, susceptibility $\chi$ (\textit{T}), and single crystal x-ray diffraction (SC-XRD) that Na$_{2.7}$Ru$_4$O$_9$ with the monoclinic tunnel type lattice (space group $C$2/$m$) exhibits an unconventional CO at room temperature while retaining metallicity. The temperature-dependent SC-XRD results show successive phase transitions with super-lattice reflections at \textbf{q}$_1$=(0, $\frac{1}{2}$, 0) and \textbf{q}$_2$=(0, $\frac{1}{3}$, $\frac{1}{3}$) below $T_{\textrm{C2}}$ (365 K) and only at \textbf{q}$_1$=(0, $\frac{1}{2}$, 0) between $T_{\textrm{C2}}$ and $T_{\textrm{C1}}$ (630 K). We interpreted these as an evidence for the formation of an unconventional CO. It reveals a strong first-order phase transition in the electrical resistivity at $T_{\textrm{C2}}$ (cooling) = 345 K and $T_{\textrm{C2}}$ (heating) = 365 K. We argue that the origin of the phase transition is due to the localized 4$d$ Ru-electrons. The results of our finding reveal an unique example of Ru$^{3+}$/Ru$^{4+}$ mixed valance heavy \textit{d}$^4$ ions.

(Invited) Technology Trend of Poly-Si TFT from Viewpoints of Crystallization and Device Performance

TFTs utilizing the Low-Temperature Polycrystalline-Si (LTPS) are very crucial for the system-on-glass. The requirements for the LTPS are a high quality, a large grain size and a position control of the nucleation. To satisfy those requirements, the promising crystallization methods have been presented. In addition, the device structures such as the double gate TFT and the tunnel type TFT have been developed. The excimer laser annealing provided a large grained film with a high-quality. It was also clarified that hydrogens in a-Si film greatly accelerated the crystal velocity and improved the crystallinity of the poly-Si film. A soft X-ray crystallization (SXC) reduced the threshold temperature of crystallization for a-Si, Ge and SixGe1-x films by 100-150 oC as compared with the thermal crystallization. Although the high-performance TFT utilizing the large single crystalline grains has been intensively researched, it does not successfully operate from the productive viewpoint. Tunneling Dielectric Thin-Film Transistor (TDTFT) was proposed and fabricated. It reduced the gate-off current less than 1/10 in comparison with a conv. TFT. In addition, the TDTFT improved the hump effect. We conclude that TDTFT will be suitable as a promising candidate of the next generation poly-Si TFT structure.

Two noncentrosymmetric polyphosphates featuring infinite one-dimensional (PO3)∞ chain, LiMP2O6 (M = Rb, Cs): Synthesis, structure and optical properties

Two noncentrosymmetric polyphosphates, namely LiCsP2O6 and LiRbP2O6 have been synthesized from the high temperature solution. The structural analysis suggests that both of them crystallize in orthorhombic space group Fdd2 (No.43), with lattice parameters: a = 18.517(4) Å, b = 19.037(4) Å, c = 13.011(3) Å, and Z = 32 for LiRbP2O6, while a = 19.009(13) Å, b = 19.402(13) Å, c = 13.180(9) Å, and Z = 32 for LiCsP2O6. In the structure, the PO4 polyhedra are connected through corner-sharing to form 1D infinite (PO3) ∞ chains stretching along the c axis, which are further linked by the LiO4 polyhedra to construct a 3D framework with two types of tunnels. And the Rb/Cs atoms are filled in or around the periphery of the tunnels to keep the charge equilibrium. The IR spectra verify their structural validity. In addition, other characterizations including the UV−vis−NIR diffuse reflectance spectra, as well as first-principles theoretical studies have been performed on the two compounds.

The comparison on resistance performance and running attitude of asymmetric catamaran changing shape of tunnel stern exit region

Catamaran vessels have been used for various purposes such as leisure craft and research vessel. Especially, asymmetric catamaran has a half of the symmetrical hull and flat side of facing inward demi-hull, and has feature of planing hulls such as hard chine, spray rail. Therefore, these vessels can travel at high speed with better stability and resistance performance. However, these features cause asymmetric catamaran to have large trim angle at high-speed condition, which cause problem on vessel’s operation performances such as visibility and dynamic instability motion. To overcome these negative effects, tunnel shape in stern has been introduced. By applying this shape, trim angles are also suppressed because large dynamic lift developed on the exit region of tunnel stern. In this research, tunnel stern was applied on the asymmetric high-speed catamaran to evaluate vessel’s hydrodynamic performance by numerical method, and the tunnel stern types are distinguished by slope of tunnel exit region: flat or narrow types. Consequently, it is confirmed that the total resistance of tunnel types is lower about 1.6∼5.0% than the bare hull in the wide speed range while showing almost same phase with the bare hull after FnV=2.3. Also, narrow type improves resistance performance further than flat type. On the other hand, trim angles show different trend with each tunnel type. In case of narrow type, the trim angle is stabilized after FnV=1.8 while that of flat type show an increasing trend as ship speed increase. These indicated that the narrow type has better resistance and operation performance than others.

In situ growth of β-FeOOH on hierarchically porous carbon as anodes for high-performance lithium-ion batteries

Sugarcane bagasse, a waste product of the sugarcane industry can be used as a precursor for the preparation of carbon. In this study, a composite consisting of hierarchically functionalized porous carbon (FPC) and β-FeOOH was synthesized via a simple and effective hydrolysis method. The hydrothermal process before the carbonization and activation of the bagasse maintained the hierarchical interconnected porous structure of the sugarcane bagasse. A nitric acid (HNO3) functionalization treatment enabled an in-situ growth of β-FeOOH on the hierarchically structured bagasse. When tested as an anode for lithium-ion batteries, the obtained FPC/β-FeOOH composite showed a high discharge capacity of 898.8 mAh g−1 at 0.2 A g−1 after 350 cycles and achieved a specific capacity of 446.1 mAh g−1 at a current rate of 1 A g−1 after 1000 cycles together with a remarkable coulombic efficiency of 99.9%. This excellent electrochemical performance of the FPC/β-FeOOH composite can be attributed to the synergistic effect of the interconnected porous structure of porous carbon and the electrochemically active tunnel type β-FeOOH nanorods. The strategy developed here is promising in design and fabrication of other composites having interconnected porous structures with high performance.

Redox Activity of Sodium Vanadium Oxides towards Oxidation in Na Ion Batteries.

The search for new materials that could be used as electrode material for Na-ion batteries is one of the most challenging issues of today. Many transition metal oxide families as well as transition metal polyanionic frameworks have been proposed over the last five years. In this work, we report the sodium extraction from Na2V3O7, which is a tunnel type structure built of [V3O7]2−∞ nanotubes held by sodium ions. We report a reversible charge capacity of 80 mAh/g at 2.8 V vs. Na+/Na due to the V5+/V4+ redox activity. No oxygen redox activity has been observed for this material nor for the vanadium (5+) oxide Na4V2O7.

Enhancement in alternating current conductivity of polypyrrole by multi-walled carbon nanotubes via single electron tunneling

To enhance alternating current (ac) conductivity of polypyrrole (PPy), multi-walled carbon nanotubes (MWCNT) are used to prepare polypyrrole-multi-walled carbon nanotube (PMCN) composites. PPy synthesized by chemical oxidative polymerization and MWCNT prepared by arc discharge were mechanically mixed to prepare two PMCN composites of mass ratios 0.95:0.05 (PMCN-1) and 0.90:0.1 (PMCN-2) respectively. The FTIR studies confirmed strong interaction between PPy and MWCNT in the composites. Highly crystalline nature of PMCN-2 composite in which MWCNT is wrapped around by PPy confirmed from XRD, FESEM and TEM analyses. Significant increase in ac conductivity of PMCN-2 composite by four orders of magnitude due to greater increase in effective degree of electron delocalization in it confirmed. High values of real dielectric constant (ε′) and dielectric loss (tanδ) at low frequency for PPy and the composites due to Maxwell-Wagner polarization, a semicircular complex plane impedance plot for PMCN-2 composite reminiscent of Debye model confirmed. Theoretical interpretation of charge transport mechanism in the composites as due to single electron tunneling as against that in PPy as due to hopping of polarons discussed thoroughly. Composites showing single electron tunneling type of charge transport have potential for production of multi functional semiconductor and superconducting devices.

Ballast water high-efficiency allocation optimisation modelling with dynamic programming for revolving floating cranes

ABSTRACTBallasting with water tanks is essential for improving the efficiency, cost and safety of lifting operation with revolving floating cranes. An optimisation model of ballast water high-efficiency adjustment was presented for the tube tunnel type ballast system. The water level variation of each ballast tank during ballasting process, the ballast water filling mass from sea before lifting and discharging mass after lifting operation are taken as optimisation variables, the minimal ballasting time during lifting process as the optimisation objective, and keeping the hull balance and stability in the lifting process as the constraint conditions. The ballast water allocation optimisation can be characterised by a multi-step decision process, and a dynamic programming method is presented which divides the decision stages based on the crane revolving angles in the rotary lifting process. An example is given to illustrate and analyse the proposed model and approach.

An analytical solution for design of pressure tunnels considering seepage loads

• In this paper, an analytical solution is proposed, for design of pressure tunnels. • The problem is considered as axial-symmetric. • The medium is assumed to be poroelastic, homogeneous and isotropic. • The applicability of it is illustrated by using illustrative example problems. In a pressure tunnel with a permeable lining, development of flow from the tunnel induces seepage stresses in the surrounding ground and the lining. In this paper, an analytical solution for analysis and design of pressure tunnels is presented, based on a generalized effective stress principle. The problem is considered as axial-symmetric, and the lining and the rock mass are assumed to be poroelastic, homogeneous and isotropic. The proposed method covers various types of pressure tunnels, such as unlined, shotcrete lined, concrete lined, reinforced concrete lined and prestressed concrete lined pressure tunnels. For unlined and uncracked lined pressure tunnels, the hydraulic analysis is independent of mechanical responses; thus, closed-form expressions for stresses, strains and pore pressure are derived. On the other hand, in cracked reinforced concrete linings, the development of cracks are considered in the mechanical and hydraulic responses. In this case, the hydraulic and mechanical analyses are coupled; therefore, the hydraulic and mechanical analyses are carried out by an iterative procedure. The applicability of the proposed solution for the design of pressure tunnels is illustrated and discussed by using an illustrative example problem.

Synthesis, crystal structure and ionic conduction of the new alluaudite Na3Bi2(AsO4)3

Transparent single crystals of alluaudite – type sodium (I) bismuth (III) trisorthoarsenate (V), Na3Bi2(AsO4)3, have been prepared by solid state reaction and have been characterized by X-ray diffraction techniques, infrared spectroscopy and scanning electron microscopy. The title compound crystallizes in the monoclinic space group, C2/c, with a = 13.673 (2) Å; b = 13.474 (3) Å; c = 6.885 (2) Å, β = 116.22 (2)°, V = 1137.9 Å3 and Z = 4. The main structural feature is the presence of infinite chains of edge-sharing Bi2O10 dimers, which are linked together by AsO4 tetrahedra, leading to a three –dimensional open framework enclosing two types of tunnels where Na+ cations lodge. The structural model was confirmed by both bond valence sum (BVS) and charge distribution (CHARDI) methods. The conductivity measurements of the compound were carried out from 250 to 500 °C using a frequency response analyzer. The conductivity of the sample at 350 °C is 1.30 × 10−5 S cm−1 and the activation energy is Ea = 0.85 eV. Compared with other sodium-ion conductors studied previously, the investigated material Na3Bi2(AsO4)3 is a medium cation conductor.

Seismic Stability of a Tunnel Considering the Dynamic Geologic Parameters of Loess

In this study, Taiyuan loess is used in the analysis of the seismic stability of a loess tunnel. This analysis considers the dynamic parameters of the loess as determined via triaxial compression tests in the literature. In this analysis, the consolidation pressure is converted into the thickness of the overlying loess layer. The spring stiffness and damping coefficients of the viscoelastic boundary are obtained using the maximum dynamic elastic modulus in conjunction with different loess moisture contents and Poisson’s ratios. Additionally, the loess cohesion and internal friction angle are also obtained for different moisture contents. By (1) utilizing the dynamic finite element static shear strength reduction method and the non-convergence rule, (2) taking the safety factor as the assessment standard for loess tunnel stability, and (3) reducing the dynamic parameters of the loess mass until the model calculation is non-convergent, the effects of the moisture content, seismic intensity and loess thickness on the safety factor are obtained. A theoretical basis for the seismic response analysis of this type of loess tunnel is provided by considering the dynamic parameters of loess.

Polygonization of Point Cloud of Tunnels Using Lofting Operation

This paper proposes a novel method for polygonizing scanned point cloud data of tunnels to feature-preserved polygons to be used for maintenance purposes. The proposed method uses 2D cross-sections of structures and polygonizes them by a lofting operation. In order to extract valid cross-sections from the input point cloud, center lines and orthogonal planes are used. Center lines of the point cloud are extracted using local symmetry analysis. In addition, this research segments a point cloud of a tunnel into lining concrete, road, and other facilities. The results of applying the proposed method to the point clouds of three types of tunnels are demonstrated, and the advantages and limitations of the proposed method are discussed.

A multiple-fan active control wind tunnel for outdoor wind speed and direction simulation.

This article presents a new type of active controlled multiple-fan wind tunnel. The wind tunnel consists of swivel plates and arrays of direct current fans, and the rotation speed of each fan and the shaft angle of each swivel plate can be controlled independently for simulating different kinds of outdoor wind fields. To measure the similarity between the simulated wind field and the outdoor wind field, wind speed and direction time series of two kinds of wind fields are recorded by nine two-dimensional ultrasonic anemometers, and then statistical properties of the wind signals in different time scales are analyzed based on the empirical mode decomposition. In addition, the complexity of wind speed and direction time series is also investigated using multiscale entropy and multivariate multiscale entropy. Results suggest that the simulated wind field in the multiple-fan wind tunnel has a high degree of similarity with the outdoor wind field.

The Research on Tunnel Surrounding Rock Classification Based on Geological Radar and Probability Theory

In order to effectively classify the surrounding rock types of tunnels, a multi-factor tunnel surrounding rock classification method based on GPR and probability theory is proposed. Geological radar was used to identify the geology of the surrounding rock in front of the face and to evaluate the quality of the rock face. According to the previous survey data, the rock uniaxial compressive strength, integrity index, fissure and groundwater were selected for classification. The related theories combine them into a multi-factor classification method, and divide the surrounding rocks according to the great probability. Using this method to classify the surrounding rock of the Ma’anshan tunnel, the surrounding rock types obtained are basically the same as those of the actual surrounding rock, which proves that this method is a simple, efficient and practical rock classification method, which can be used for tunnel construction.

Investigation of α-MnO2 Tunneled Structures as Model Cation Hosts for Energy Storage.

Future advances in energy storage systems rely on identification of appropriate target materials and deliberate synthesis of the target materials with control of their physiochemical properties in order to disentangle the contributions of distinct properties to the functional electrochemistry. This goal demands systematic inquiry using model materials that provide the opportunity for significant synthetic versatility and control. Ideally, a material family that enables direct manipulation of characteristics including composition, defects, and crystallite size while remaining within the defined structural framework would be necessary. Accomplishing this through direct synthetic methods is desirable to minimize the complicating effects of secondary processing. The structural motif most frequently used for insertion type electrodes is based on layered type structures where ion diffusion in two dimensions can be envisioned. However, lattice expansion and contraction associated with the ion movement and electron transfer as a result of repeated charge and discharge cycling can result in structural degradation and amorphization with accompanying loss of capacity. In contrast, tunnel type structures embody a more rigid framework where the inherent structural design can accommodate the presence of cations and often multiple cations. Of specific interest are manganese oxides as they can exhibit a tunneled structure, termed α-MnO2, and are an important class of nanomaterial in the fields of catalysis, adsorption-separation, and ion-exchange. The α-MnO2 structure has one-dimensional 2 × 2 tunnels formed by corner and edge sharing manganese octahedral [MnO6] units and can be readily substituted in the central tunnel by a variety of cations of varying size. Importantly, α-MnO2 materials possess a rich chemistry with significant synthetic versatility allowing deliberate synthetic control of structure, composition, crystallite size, and defect content. This Account considers the investigation of α-MnO2 tunnel type structures and their electrochemistry. Examination of the reported findings on this material family demonstrates that multiple physiochemical properties influence the electrochemistry. The retention of the parent structure during charge and discharge cycling, the material composition including the identity and content of the central cation, the surface condition including oxygen vacancies, and crystallite size have all been demonstrated to impact electrochemical function. The selection of the α-MnO2 family of materials as a model system and the ability to control the variables associated with the structural family affirm that full investigation of the mechanisms related to active materials in an electrochemical system demands concerted efforts in synthetic material property control and multimodal characterization, combined with theory and modeling. This then enables more complete understanding of the factors that must be controlled to achieve consistent and desirable outcomes.

Results of research into technological process of fruit drying in the solar dryer

The work addresses the issue of solving a scientific-applied task on the substantiation of operation modes of the solar fruit dryer in order to improve energy efficiency of the technological process of fruit drying for small amounts of fruit processed at private farms. We have explored the use of solar energy for fruit drying at the latitude of the location of Rivne oblast, Ukraine, which has the average annual solar radiation power of the order of 3.41 kW∙h/m 2 per daylight. This makes it possible to receive from 1.5 to 2.3 kW∙h of energy per day from the air collector area of 1 m 2 . The series of analytical and experimental studies that we conducted has confirmed the possibility for a significant intensification of the process of fruit drying in the solar dryer. Compared with modern convective drying devices, the specific energy consumption when drying the fruit in the solar dryer is reduced by 3…3.7 MJ/kg. The degree of intensification grows by 3.3…12 times compared to drying devices of the mine and tunnel types. Such results were achieved by implementing the proposed design of a flat mirror concentrator, to enhance the slanting fluxes of morning and evening sun irradiation, and a heat accumulator, based on pebbles, for accumulating at night the excessive heat from the reserve source of energy. It was established that regardless of a blanching technique for fruit raw materials, the duration of drying in the solar dryer varies depending on physical parameters of the environment. In the process of drying, the experiments were carried out at a temperature of 289.15…333.15 K, and the duration of drying was from 50 to 74 hours. We have analyzed the effect of operational parameters on a change in the chemical indicators and quality of the dried fruit. Specifically, the content of vitamin C, which was 5.2 mg/% for pear, and 4.3 mg/% for apple. The acidity was 0.29 % for pear, and 0.46 % for apple. The content of dry nutrients was 87.5 % for pear, and 85.9 % for apple. The sugar content of fruit raw materials was 59.36 % for pear, and 57.8 % for apple.

Experimental and numerical analysis of flow field and ventilation performance in a traffic tunnel ventilated by axial fans

To investigate air flow in longitudinally ventilated traffic tunnels, a scaled model of a typical road-traffic tunnel with an appropriate ventilation system based on axial ducted fans, is designed and built in the Lab. The focus of this paper is the airflow in a bi-directional traffic, two-lane tunnel. At the scale ratio of approx. 1:20, at 20.52m length it represents ? 400m of a realscale tunnel. The model consists of two parallel tunnel tubes, where the main tunnel (with a hydraulic diameter of ???1 ? 0.4m) has the geometry of a scaled road traffic-tunnel. The second tunnel (???2 ? 0.16m) has a smaller size and is circular in cross-section, used only to simulate airflow towards an evacuation tunnel tube. Thus the two tunnels are connected by the evacuation passages, equipped with adjustable escape doors. By a combination of experimental and numerical work, the air flow-field and the performance of the ventilation system are investigated. The velocity field and its turbulence properties exiting the fans were determined experimentally using hot-wire anemometry. These data were further processed to be used in the tunnel flow computations by CFD. The efficiency of momentum transfer (????, Kempf factor) of the longitudinal tunnel ventilation is determined. The effect that the imposed boundary conditions and the level of their detail, have within a CFD computation of tunnel airflow, with respect to accuracy, velocity distribution and computed ????. Finally a traffic-loaded (traffic ?jam?) case of flow is studied through experiment and CFD. The difficulty in assessing the required thrust of the plant in traffic-jam tunnel conditions is discussed, and the ventilation efficiency is estimated. Based on later results, the two limiting shapes of axial velocity distribution with respect to height above the road, in this type of tunnel and traffic, are estimated. The last result can be used as a realistic boundary condition (as inlet b.c. and/or initial condition) for numerical studies of flow and fire scenarios in such tunnels with the traffic load critical for design.

Synthesis and crystal structure of two new phosphates with Alluaudite type structure: (M, Mn)3Fe(PO4)3 (M= Ca, Cd)

Two new phosphates with alluaudite type structure (M, Mn)3Fe(PO4)3 (M= Ca, Cd), namely Ca1.54Mn1.46Fe(PO4)3 and Cd0.66Mn2.34Fe(PO4)3, has been synthesized by a solid state reaction and characterized by single-crystal X-ray diffraction. The two compounds crystallize in the monoclinic system with C2/c space group. Their open framework results from (Fe1/Mn1)2O10 units of edge-sharing (Fe/Mn)O6 octahedra, which alternate with M(1)O6 octahedra (M(1)=Ca1/Mn2 or Cd1/Mn2) that form infinite chains running along [10-1] direction. These chains are linked together through the common corners of PO4 tetrahedra giving rise to two types of tunnels occupied by bivalent cations Ca2+ or Cd2+ and Mn2+.