Horizontal Barrier Research Articles

Crossing safety barriers: Influence of children’s morphological and functional variables

Thirty-three children between 3 and 6 years of age were asked to climb four different types of safety barriers. Morphological and functional variables of the children, which were expected to influence climbing or passing through skills, were collected. The influence of those variables on children’s success rate and time to cross was tested. No barrier offered a total restraining efficacy. The horizontal bars barrier was crossed by 97% of the children. In the group of children that succeeded in crossing the four barriers, mean time to cross the most difficult barrier was 15 s. Age was the best predictor for success in crossing most barriers but morphology and strength were important predictors of time to cross. The influence of anthropometric variables in time to cross was dependent upon the characteristics of the barrier. A good design of safety barriers should consider children’s age, morphology and strength.

Effects of Recharge Wells and Flow Barriers on Seawater Intrusion

The installation of recharge wells and subsurface flow barriers are among several strategies proposed to control seawater intrusion on coastal groundwater systems. In this study, we performed laboratory-scale experiments and numerical simulations to determine the effects of the location and application of recharge wells, and of the location and penetration depth of flow barriers, on controlling seawater intrusion in unconfined coastal aquifers. We also compared the experimental results with existing analytical solutions. Our results showed that more effective saltwater repulsion is achieved when the recharge water is injected at the toe of the saltwater wedge. Point injection yields about the same repulsion compared with line injection from a screened well for the same recharge rate. Results for flow barriers showed that more effective saltwater repulsion is achieved with deeper barrier penetration and with barriers located closer to the coast. When the flow barrier is installed inland from the original toe position however, saltwater intrusion increases with deeper barrier penetration. Saltwater repulsion due to flow barrier installation was found to be linearly related to horizontal barrier location and a polynomial function of the barrier penetration depth.

Leakage from gravity currents in a porous medium. Part 1. A localized sink

We consider the buoyancy-driven flow of a fluid injected into a semi-infinite porous medium bounded by a horizontal impermeable barrier through which a single localized sink allows leakage of the injected fluid. Our study is motivated by the geological sequestration of carbon dioxide (CO2), which is less dense than the ambient water, and the possibility that fissures in the bounding ‘cap’ rock may therefore compromise the long-term storage of CO2. A theoretical model is presented in which the leakage through the sink, or fissure, is driven by the hydrostatic pressure at the sink of the injected buoyant fluid. We determine numerical solutions for the evolution of the gravity current in the porous medium and for the quantity of fluid that escapes through the sink as a function of time. A quantity of considerable interest is the efficiency of storage, which we define as the flux of fluid that is stably stored relative to the amount injected. At the later stages in the evolution of the current, the region near the source and sink reaches a quasi-steady state. We find analytical solutions to this asymptotic state which show that the efficiency of storage decreases to zero like 1/lnt, where t is the time since initiation of the current, and predict a dependence on the properties of the sink in agreement with our numerical results. The implications of this result for the geological sequestration of CO2 are discussed.

The Capacitated Location-Allocation Problem in the Presence of <i>k</i> Connections

We consider a capacitated location-allocation problem in the presence of k connections on the horizontal line barrier. The objective is to locate a set of new facilities among a set of existing facilities and to allocate an optimal number of existing facilities to each new facility in order to satisfy their demands such that the summation of the weighted rectilinear barrier distances from new facilities to existing facilities is minimized. The proposed problem is designed as a mixed-integer nonlinear programming model. To show the efficiency of the model, a numerical example is provided. It is worth noting that the global optimal solution is obtained.

Study of the seasonal ozone variations at European high latitudes

The geographic area at high latitudes beyond the polar circle is characterized with long darkness during the winter (polar night) and with a long summertime insolation (polar day). Consequentially, the polar vortex is formed and the surrounding strong polar jet is characterized by a strong potential vorticity gradient representing a horizontal transport barrier. The ozone dynamics of the lower and middle stratosphere is controlled both by chemical destruction processes and transport processes. To study the seasonal ozone variation at high latitudes, ozone vertical distributions are examined, collected from the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) (69.3°N, 16.0°E,) station at Andenes and from the stations at Sodankylä (67.4°N, 26.6°E) and at Ny-Ålesund (78.9°N, 11.9°E). The data sets cover the time period from 1994 until 2004. We find a second ozone maximum near 13–15 km, between the tropopause and the absolute ozone maximum near 17–20 km. The maximum is built up by the combination of air mass transport and chemical ozone destruction, mainly caused by the NO x catalytic cycle, which begins after the polar night and intensifies with the increasing day length. Formation of a troposphere inversion layer is observed. The inversion layer is thicker and reaches higher altitudes in winter rather than in summer. However, the temperature inversion during summer is stronger. The formation of an enhanced ozone number density is observed during the spring–summer period. The ozone is accumulated or becomes poor by synoptic weather patterns just above the tropopause from spring to summer. In seasonal average an ozone enhancement above the tropopause is obtained. The stronger temperature inversion during the summer period inhibits the vertical stratosphere–troposphere exchange. The horizontal advection in the upper troposphere and lower stratosphere is enforced during summer. The combination of these mechanisms generates a layer with a very low ozone number density above the troposphere inversion layer subsisting from June/July until the late autumn.

Dichotomy for the Hausdorff dimension of the set of nonergodic directions

Given an irrational 0<λ<1, we consider billiards in the table P λ formed by a $\tfrac{1}{2}\times1$ rectangle with a horizontal barrier of length $\frac{1-\lambda}{2}$ with one end touching at the midpoint of a vertical side. Let NE (P λ ) be the set of θ such that the flow on P λ in direction θ is not ergodic. We show that the Hausdorff dimension of NE (P λ ) can only take on the values 0 and $\tfrac{1}{2}$ , depending on the summability of the series $\sum_{k}\frac{\log\log q_{k+1}}{q_{k}}$ where {q k } is the sequence of denominators of the continued fraction expansion of λ. More specifically, we prove that the Hausdorff dimension is $\frac{1}{2}$ if this series converges, and 0 otherwise. This extends earlier results of Boshernitzan and Cheung.

Influence of large-scale inhomogeneities on a construction dewatering system in chalk

Large-scale anisotropy and inhomogeneities resulting from the presence of fissures, fractures and high-permeability zones can have a major impact on local groundwater flows, and affect significantly the performance of a construction dewatering system. A groundwater model for the HS1 Channel tunnel rail link Thames tunnel southern approach excavation is used to show that the observed performance of the construction dewatering system cannot adequately be explained unless such features are incorporated. While experience suggested that such features were likely to be present in this geological setting, at the design stage there was significant uncertainty regarding their scale. Groundwater flow modelling enabled the location and extent of the inhomogeneities present to be deduced in some detail. Features such as highly permeable zones might be identified by more thorough site investigation, including the more widespread use of pumping tests. However, the influence of anisotropy is harder to establish, primarily because its effect is most significant once a horizontal flow barrier (for example, a retaining wall) is in place, which is generally not the case during site investigation.

Duck! Scaling the height of a horizontal barrier to body height

Recent research shows that the body is used to scale environmental extents. We question whether the body is used to scale heights as measured by real actions (Experiments 1 and 2) or by judgments about action and extent made from a single viewpoint (Experiments 3 and 4). First, participants walked under barriers naturally, when wearing shoes, or when wearing a helmet. Participants required a larger margin of safety (they ducked at shorter heights) when they were made taller. In follow-up experiments, participants visually matched barrier heights and judged whether they could walk under them when wearing shoes or a helmet. Only the helmet decreased visually matched estimates; action judgments were no different when participants' eye height increased. The final experiment suggested that the change in matched estimates may have been due to lack of experience wearing the helmet. Overall, the results suggest that perceived height is scaled to the body and that when body height is altered, experience may moderate the rescaling of height.

The effect of a fissure on storage in a porous medium

We consider the two-dimensional buoyancy driven flow of a fluid injected into a saturated semi-infinite porous medium bounded by a horizontal barrier in which a single line sink, representing a fissure some distance from the point of injection, allows leakage of buoyant fluid. Our studies are motivated by the geological sequestration of carbon dioxide (CO2) and the possibility that fissures in the cap rock may compromise the safe long-term storage of CO2. A theoretical model is presented that accounts for leakage through the fissure using two parameters, which characterize leakage driven both by the hydrostatic pressure within the overriding fluid and by the buoyancy of the fluid within the fissure. We determine numerical solutions for the evolution of both the gravity current within the porous medium and the volume of fluid that has escaped through the fissure as a function of time. A quantity of considerable practical interest is the efficiency of storage, which we define as the amount of fluid remaining in the porous medium relative to the amount injected. This efficiency scales like t−1/2 at late times, indicating that the efficiency of storage ultimately tends to zero. We confirm the results of our model by comparison with an analogue laboratory experiment and discuss the implications of our two-dimensional model of leakage from a fissure for the geological sequestration of CO2.

De Finetti’s optimal dividends problem with an affine penalty function at ruin

In a Lévy insurance risk model, under the assumption that the tail of the Lévy measure is log-convex, we show that either a horizontal barrier strategy or the take-the-money-and-run strategy maximizes, among all admissible strategies, the dividend payments subject to an affine penalty function at ruin. As a key step for the proof, we prove that, under the aforementioned condition on the jump measure, the scale function of the spectrally negative Lévy process has a log-convex derivative.

The horizontal barrier effect of stems on the foraging behaviour of cattle grazing five tropical grasses

The rate of nutrient intake (RNI) is a primary determinant of animal performance in grazing cattle and depends on both diet quality and instantaneous intake rate (IIR). In turn, diet quality and IIR are a function of the foraging behaviour of the animal (selectivity, bite mass and bite rate) and the characteristics of the sward. In this study we evaluated the effect of the stem density and the tensile resistance of stems on the foraging behaviour of cattle grazing tropical pasture species. The methodology involved the use of small sown microswards offered to tethered cattle. The experiment consisted of a factorial combination of five tropical grasses [ Bothriochloa pertusa (Bp), Chloris barbata (Cb), Chloris gayana (Cg), Cynodon dactylon (Cd) and Heteropogon contortus (Hc)] and three stem densities (0, 400 and 800 stems m − 2 ). Bp and Cd had stems of significantly lower tensile resistance (19 and 15 N respectively) (Group 1) than those of Cb, Cg and Hc (110, 211 and 167 N respectively) (Group 2). The steers avoided stems of Group 2 and thus, reduced bite area, bite mass, IIR and RNI as stem density increased. However, the animals did not avoid stems of Group 1 and there was no effect of stem density on any of the foraging behaviour variables when cattle grazed species in Group 1. These results confirm that RNI and plant part selection is closely associated with the tensile resistance of the stem.

Tariffs, Horizontal Regulatory Standards and Protection against Foreign Competitors

This paper focuses on a regulator's choice between setting a pure, horizontal technical barrier to trade (HTBT) or a tariff in a linear, Cournot duopoly, where a foreign firm competes with a local rival. Where a country is free to impose a tariff, it will not impose a HTBT. Only under a limited set of circumstances will the profit-shifting effect be sufficient to lead to total exclusion of the foreign firm: in other conditions, the country will set a tariff yielding some revenue. By contrast, if tariffs are constrained by international agreement, then the importing country will set an HTBT to exclude the foreign firm if and only if tariffs are reduced below a threshold level. Trade liberalisation agreements which only cover tariffs can reduce, rather than increase global welfare.

Hidraulic potential anomaly indicating thermal water reservoir and gas pool near Berekfürdő, Trans-Tisza Region, Hungary

Abstract In the surroundings of Berekfurdő (Trans-Tisza Region) a significant positive anomaly was observed in the fluid potential field, in the course of a regional-scale hydrogeologic study of the Great Hungarian Plain (Toth and Almasi 2001). It was assumed that the cause of this phenomenon could be the presence of structural elements in an overpressured fluid potential field. The seismic, hydraulic and hydrogeochemical evaluation of the anomaly proved the presence of a complex structure. The results furnish an example for the theoretical model of Matthai and Roberts (1996). The identified faults, which define the basement high and rise close to the surface, represent direction-dependent control over the fluid flow systems of the Study Area. The detected horizontal barrier fault zones may act as lateral seals of the Tatarules-Kunmadaras gas field and might ensure the active water pressure of the reservoir system. The junction of the vertically conducting and horizontally sealing fault zones near Berekfu...

Cryogenic capillary screen heat entrapment

Cryogenic liquid acquisition devices (LADs) for space-based propulsion interface directly with the feed system, which can be a significant heat leak source. Further, the accumulation of thermal energy within LAD channels can lead to the loss of subcooled propellant conditions and result in feed system cavitation during propellant outflow. Therefore, the fundamental question addressed by this program was: “To what degree is natural convection in a cryogenic liquid constrained by the capillary screen meshes envisioned for LADs?” Testing was first conducted with water as the test fluid, followed by liquid nitrogen (LN 2) tests. In either case, the basic experimental approach was to heat the bottom of a cylindrical column of test fluid to establish stratification patterns measured by temperature sensors located above and below a horizontal screen barrier position. Experimentation was performed without barriers, with screens, and with a solid barrier. The two screen meshes tested were those typically used by LAD designers, 200 × 1400 and 325 × 2300, both with Twill Dutch Weave. Upon consideration of both the water and LN 2 data, it was concluded that heat transfer across the screen meshes was dependent upon barrier thermal conductivity and that the capillary screen meshes were impervious to natural convection currents.

On a risk model with debit interest and dividend payments

We consider the compound Poisson risk model with debit interest and dividend payments. The model assumes that the company is allowed to borrow at some debit interest rate when the surplus turns negative, and that the premium incomes are paid out as dividends to shareholders when the surplus reaches a horizontal barrier of level b . We first derive integro-differential equations for the expected discounted value of all dividends until absolute ruin, V b ( u ) , which is twice continuously differentiable. In the case of exponential claim amounts, we obtain explicit expressions for V b ( u ) and the optimal barrier b ∗ which maximizes V b ( u ) . We then perform a similar study for the Gerber–Shiu expected discounted penalty function. Again, when claims are exponentially distributed, we are able to find explicit expressions for the joint distribution of the surplus just prior to absolute ruin and the deficit at absolute ruin, which is a special case of the Gerber–Shiu function.

Perception of Affordances for Walking Under a Barrier From Proximal and Distal Points of Observation

We investigated perception of affordances for a given behavior from points of observation other than that from which the behavior is to be performed. Participants viewed a horizontal barrier from different points of observation and reported whether they would be able to walk under that barrier. In Experiment 1, they viewed the barrier both while standing on the floor and while sitting on the floor. In Experiment 2, they viewed the barrier both while standing on the floor and while standing on a step stool. The results show that although perception of this affordance is body-scaled regardless of point of observation, there are subtle differences in the perceptual boundaries in each case. Such differences are likely due to differential attunement to the information specifying the affordance at each point of observation.

On Exact Solutions for Dividend Strategies of Threshold and Linear Barrier Type in a Sparre Andersen Model

For the classical Cramér-Lundberg risk model, a dividend strategy of threshold type has recently been suggested in the literature. This strategy consists of paying out part of the premium income as dividends to shareholders whenever the free surplus is above a given threshold level. In contrast to the well-known horizontal barrier strategy, the threshold strategy can lead to a positive infinite-horizon survival probability, with reduced profit in terms of dividend payments. In this paper we extend several of these results to a Sparre Andersen model with generalized Erlang(n)-distributed interclaim times. Furthermore, we compare the performance of the threshold strategy to a linear dividend barrier model. In particular, (partial) integro-differential equations for the corresponding ruin probabilities and expected discounted dividend payments are provided for both models and explicitly solved for n = 2 and exponentially distributed claim amounts. Finally, the explicit solutions are used to identify parameter sets for which one strategy outperforms the other and vice versa.

On Exact Solutions for Dividend Strategies of Threshold and Linear Barrier Type in a Sparre Andersen Model

For the classical Cramér-Lundberg risk model, a dividend strategy of threshold type has recently been suggested in the literature. This strategy consists of paying out part of the premium income as dividends to shareholders whenever the free surplus is above a given threshold level. In contrast to the well-known horizontal barrier strategy, the threshold strategy can lead to a positive infinite-horizon survival probability, with reduced profit in terms of dividend payments. In this paper we extend several of these results to a Sparre Andersen model with generalized Erlang(n)-distributed interclaim times. Furthermore, we compare the performance of the threshold strategy to a linear dividend barrier model. In particular, (partial) integro-differential equations for the corresponding ruin probabilities and expected discounted dividend payments are provided for both models and explicitly solved for n = 2 and exponentially distributed claim amounts. Finally, the explicit solutions are used to identify parameter sets for which one strategy outperforms the other and vice versa.

Numerical investigation of the gel barrier formation with vertical injection pipe

Permeation grouting is the injection of a fluid grout into ground and production of a solidified mass to carry increased load and/or fill voids to control water flow. This study examined a technology of constructing horizontal gel barrier by the permeation grouting through multiple vertical injection pipes. Colloidal Silica (CS) solution was used as a gelling liquid to be injected and solidified in the unsaturated soil. Formation of a gel bulb was simulated and the results were compared with those obtained from the sleeve pipe injection with horizontal pipes. The gel bulb generated from the injection method employing vertical pipe showed greater sensitivity of the bulb’s lateral extent to variations in operating conditions compared to the sleeve pipe injection. Although in the limited numbers, in all examined cases, the vertical-pipe system appeared to consume a larger volume of CS solution than the horizontal-pipe system to form an equivalent horizontal gel barrier. This result supports our intuition that the injection with the horizontal pipes may be more effective than the one with vertical pipes in constructing horizontal gel barrier.

水平浄化壁による土壌浸透水の硝酸性窒素浄化技術

The nitrate contamination level in groundwater depends on hydrogeological properties underground as well as the agricultural system aboveground. Excessive use of nitrogen fertilizers leads to nitrate contamination of groundwater under the crop area, and the nitrate concentration level will be severe if the ground is composed of coarse material and has high permeability. The impact of nitrate reaching groundwater is also influenced by the microbial activity of anaerobes in soil that contributes denitrification.In the present state of this issue in Japan, the main governmental action for this problem is to reduce the excessive use of fertilizer and manure. However, groundwater monitoring results by the Japan Environmental Protection Agency indicates that nitrate contamination is still spreading nationwide and the nitrate concentration in groundwater has exceeded the regulation level (10 mg/L) in 5% of the monitoring wells since 1995. Therefore, development of an effective cleanup measure has been required.In this paper, pilot-scale field application of a horizontal Permeable Reactive Barrier (PRB), which is a nitrate cleanup technology for the vadose zone, is introduced. The horizontal PRB installed in this study consists of an accelerative denitrifying layer with low permeability and an organic matter supplying layer embedded on it. The low permeable layer using field soil retains a lot of water in the vadose zone because of capillary force, and a reductive condition adopted for denitrification seems to be gradually formed in the barrier. In fact, the concentration of nitrate in soil water (unsaturated condition) declined from 6-8 mg/L to less than 0.1 mg/L in the accelerative denitrifying layer without an organic matter supplying layer, and an increase of inorganic carbon (IC) content from 35 mg/L to 50 mg/L was observed. An increase of IC indicates that the field soil originally contained a significant amount of water-soluble organic matter and biological mineralization of dissolved organic matter occurred in pore water. Therefore, a low permeable soil layer with a suitable organic content acts as a denitrification layer, and installation of such a layer under the ground could be an effective measure to preserve groundwater from nitrate impact.