High Slope Angles Research Articles

Analysis of the spatial distribution of the landslides triggered by the 1923 Great Kanto Earthquake, Japan.

The Great Kanto Earthquake that occurred in the southern part of Kanto district, Japan, on September 1, 1923, was reported to have triggered numerous landslides (over 89,080 slope failures over an area of 86.32 km2). This study investigated the relationship between the landslide occurrence caused by this earthquake and geomorphology, geology, soil, seismic ground motion, and coseismic deformation. We found that a higher landslide density was mainly related to a larger absolute curvature and a higher slope angle, as well as to several geological units (Neogene plutonic rock, accretionary prism, and metamorphic rocks). Moreover, we performed decision tree analyses, which showed that slope angle, geology, and coseismic deformation were correlated to landslide density in that order. However, no clear correlation was found between landslide density and seismic ground motion. These results suggest that landslide density was greater in areas of large slope angle or fragile geology in the area with strong shaking enough to trigger landslides.

Another one bites the dust – Two street canyons studied with magnetic biomonitoring and OSPM modelling

Urban areas form a mosaic of microenvironments and structures, such as street canyons that are susceptible to elevated levels of traffic related pollutants. Street canyons are a relevant topic in air quality research and modelling since they are prone to reduced natural ventilation and when exposed to increased traffic emissions, can pose a serious risk to public health. We applied magnetic biomonitoring using moss bags to evaluate the quality of Operational Street Pollution Model (OSPM) and to study vertical distribution of modelled particulate matter (PM), magnetic PM and heavy metal pollution in a street canyon in Turku and Helsinki, Finland. Moss bags were attached on opposite sides of the streets at 3-, 6-, 9- and 12-m heights for 44 days in late autumn. Samples were analysed for mass-specific magnetic susceptibility (χ), hysteresis parameters and elemental components. High χ values and elemental concentrations of Fe, Al, Ti, Zn, Mn, Cu and Ba were found in both street canyons. Compared to measurements with airborne magnetic PM, the OSPM model underestimated the difference in PM concentrations between the opposite street canyon faces and overestimated the dilution of PM concentrations with altitude. In Turku the results between the OSPM model and magnetic measurements were incompatible. We suspect this is due to meteorological model input data from a distant weather station, street canyon features and a high slope angle contributing to non-uniform emissions in the street canyon. We demonstrate that the moss bag technique is a versatile tool to understand the small-scale variations of concentrations in a variety of complex urban environments.

Three-Dimensional Smooth Particle Hydrodynamics Modelling of Liquid–Sediment Interaction at Coastline Region

The three-dimensional liquid–sediment system of a coastline was investigated using experimental and numerical approaches. A scaled-down model of the coastline was numerically studied using smooth particle hydrodynamics (SPH). The flow dynamics and the impacts of the wave frequency and the seaward slope angle on the breaking wave characteristics of the two-phase liquid–sediment interaction were parametrically studied. A particle image velocimetry (PIV) experiment was conducted to validate the SPH predictions. It was found that the flow profiles obtained by the PIV and SPH are in good agreement both qualitatively and quantitatively. The maximum velocity of the fluid flow was recorded as 0.5623 m/s in the SPH simulation, but as 0.5860 m/s in the PIV experimental, with a percentage difference of 4.21%. Subsequently, it was found that the breaking wave characteristic is surging at the wave frequency range of f<0.15 Hz, plunging at 0.15<f<0.55 Hz, and spilling at 0.55<f≤1.0 Hz. It was also established that at a particular Froude number, it is observed that spilling, plunging, and surging wave breakers are produced at low, mid, and high seaward slope angles, respectively. Meanwhile, increasing the Froude number increases the tendency to produce spilling or plugging breaking waves, irrespective of the slope angle. Ultimately, this study has demonstrated the presented methodology’s usefulness in investigating coastlines’ liquid–sediment interaction properties.

Development of the morphodynamics on Little Ice Age lateral moraines in 10 glacier forefields of the Eastern Alps since the 1950s

Abstract. Since the end of the Little Ice Age (LIA) in the middle of the 19th century, Alpine glaciers have been subject to severe recession that is enhanced by the recent global warming. The melting glaciers expose large areas with loose sediments in the form of lateral moraines, amongst other forms. Due to their instability and high slope angle, the lateral moraines are reworked by geomorphological processes such as debris flows, slides, or fluvial erosion. In this study, the development of the morphodynamics and changes in geomorphological processes on lateral moraines were observed over decades, based on a selection of 10 glacier forefields in the Eastern Alps. To identify geomorphological changes over time, several datasets of archival aerial images reaching back to the 1950s were utilized in order to generate digital elevation models (DEMs) and DEMs of difference. The aerial images were complemented by recent drone images for selected moraine sections, enabling a high-resolution analysis of the processes currently occurring. The results concerning the development of morphodynamics on lateral moraine sections are diverse: some slopes display a stagnation of the erosion rates, whereas the rates of one section increase significantly; however, the majority of the slopes show a decline in morphodynamics over decades but stay on a high level in many cases. In particular, moraine sections with high morphodynamics at the beginning of the observation period mostly show high erosion rates up until present-day measurements, with values up to 11 cm yr−1. These moraine sections also feature heavy gullying on their upper slopes. A correlation between the development of morphodynamics and the time since deglaciation could scarcely be established. In fact, the results instead indicate that characteristics of the lateral moraines such as the initial slope angle at the time of deglaciation have a significant influence on the later morphodynamics. These observations raise concerns as to whether the until now often conducted analyses based on the comparison of lateral moraine sections with different distances to the glacier terminus, assumed to represent varying time spans since deglaciation, can provide sound evidence concerning the process of stabilization.

Исследование концентраторных фотоэлектрических модулей с отражающими элементами вторичной оптики

The characteristics of concentrator photovoltaic modules based on a 120 × 120 mm Fresnel lens with secondary concentrators in the form of hollow aluminum focons with internal mirror walls are studied. The optimal sizes and configurations of secondary concentrators are determined to increase the efficiency of focusing systems of concentrator modules. The maximum value of the allowable misorientation angle was obtained, equal to ±0.75°, corresponding to a power drop to a level of 90% relative to the maximum power value of the concentrator photovoltaic module at normal beam incidence. For a module with the most efficient focon 40 mm high and side face slope angles of 17°, the maximum efficiency of the module under laboratory conditions was obtained, equal to 35.15%. Under natural conditions, the efficiency value reached 33.8 The results obtained correspond to the level achieved for the best foreign analogues.

Erosion Control in the Tropical Rainforest Catchments using Modified Intensive Rehabilitation

Tropical rainforests in Indonesia is currently managed by Intensive Forest Management System (IFMS), characterized by selective timber harvesting and intensive rehabilitation to enrich standing stock. This study conducted quantitative evaluations on catchment scale impacts of IFMS during each selective logging (SL) and intensive rehabilitation (IR) stage. SS concentrations were measured in three headwater catchments located in tropical rainforests of the Bukit Baka Experimental Catchments, Central Kalimantan, Indonesia. While no forestry operation was conducted in catchment A, operations based on IFMS were conducted in catchments B and C. A combination among the great surface disturbance by skid trails, large tree extraction ratio, and high slope angle of catchment B resulted in the greatest SS. During the post-IR period, SS concentration of catchment B did not show decreases in comparison with that during the post-SL period. In catchment C, increases in SS concentration were observed during the post-IR period. Thus, this study indicated that IR of IFMS was not effective to decrease SS concentration in the initial stage of the post operation period, but the modified intensive rehabilitation with considering the contour and topography potentially significant to control erosion.

Quantitative investigation of the validity conditions for the Beckmann–Kirchhoff scattering model

Approximate and rigorous methods are widely used to model light scattering from a surface. The boundary element method (BEM) is a rigorous model that accounts for polarization and multiple scattering effects. BEM is suitable to model the scattered light from surfaces with complex geometries containing overhangs and re-entrant features. The Beckmann–Kirchhoff (BK) scattering model, which is an approximate model, can be used to predict the scattering behavior of slowly varying surfaces. Although the approximate BK model cannot be applied to complex surface geometries that give rise to multiple scattering effects, it has been used to model the scattered field due to its fast and simple implementation. While many of the approximate models are restricted to surface features with relatively small height variations (typically less than half the wavelength of the incident light), the BK model can predict light scattering from surfaces with large height variations, as long as the surfaces are locally flat with small curvatures. Thus far, attempts have been made to determine the validity conditions for the BK model. The primary validity condition is that the radius of curvature of any surface irregularity should be significantly greater than the wavelength of the light. However, to have the most accurate results for the BK model, quantifying the validity conditions is critical. This work aims to quantify the validity conditions of the BK model according to different surface specifications, e.g., slope angles (SA) and curvatures. For this purpose, the scattered fields from various sinusoidal and combinations of sinusoidal profiles are simulated using the BEM and the BK models and their differences are compared. The result shows that the BK model fails when there are high SA ( ⪆ 38 deg) and small radii of curvature ( ⪅ 10 λ) within a sinusoidal profile. Moreover, it is shown that for a combination of sinusoidal profiles the BK model is valid for profiles with a high maximum slope angle value ( ⪆ 38 deg) if the average of positive SA is low ( ⪅ 5 deg).

Disentangling factors controlling earthquake-triggered soft-sediment deformation in lakes

In-situ soft sediment deformation structures (SSDS) are commonly used as paleoseismic indicators in marine and lacustrine sedimentary records. Earthquake-related shear can deform sediment in the shallow subsurface through Kelvin-Helmholtz instability. The SSDS related to Kelvin-Helmholtz instability have been used to quantify shaking strength of past earthquakes. However, the relative importance of i) lithology and physical properties, ii) potential basal shear surfaces (e.g. clastic deposits), iii) slope angle, and iv) seismic shaking strength (e.g. peak ground acceleration) for deformation related to Kelvin-Helmholtz instability remains poorly studied. Lake Riñihue (south-central Chile) is chosen as a natural laboratory for disentangling the effect of the aforementioned factors because i) the sediment composition of background sediment varies downcore and ii) volcanogenic clastic deposits are abundant within the sedimentary sequence. A previous study at lake Riñihue identified 25 SSDS intervals induced by historical earthquakes of varying rupture extent in 17 sediment cores taken at slope angles ranging from ~0.2° to ~4.9° (i.e. 16 slope sites and 1 basin site). Our study shows that deformation mostly occurs directly above volcanogenic deposits (i.e. 72 % of SSDS intervals), suggesting that volcanogenic deposits promote earthquake-induced deformation by strain softening, liquefaction or water film formation. Deformation thickness of SSDS increases with higher slope angles (i.e. strong positive correlation). Additionally, deformation thickness commonly corresponds to the stratigraphic depth of the youngest preceding volcanogenic deposit, but for steeper slope angles stratigraphically older volcanogenic deposits can function as basal shear surface. Therefore, we suggest that deformation thickness is primarily regulated by gravitational stress (i.e. slope angle) and secondarily by the stratigraphic depth of volcanogenic deposits. The earthquakes related to strongest shaking caused almost exclusively SSDS with highest deformation degrees (i.e. folds and intraclast breccia) as well as largest spatial extent of SSDS, resulting in highest numbers of related SSDS in the investigated cores. Thinner SSDS have higher deformation degrees at a given shaking strength, as seismically-induced shear energy acts more effectively on thinner deforming sequences. Therefore, we suggest that deformation degree is primarily controlled by shaking strength and secondarily modulated by the thickness of the deforming sequences. We infer that deformation thickness is not a reliable indicator of paleoseismic shaking strength as this relies on many preconditioning factors independent of shaking strength. On the other hand, deformation degree can be a good proxy for shaking strength also in settings with varying lithotypes and intercalated clastic event deposits, provided multiple cores are studied to avoid under- or overestimation of paleoseismic shaking strength.

Design and Assessment of a Small-Scale Machine for Cleaning Wheat Grains

Abstract A small-scale wheat cleaning machine was designed to winnow and separate grains from materials-other-than-grains (MOG), such as premature grains and chaff, in order to enhance the quality of grains. It was evaluated technically with respect to assessment criteria: cleanliness, grain loss, chaff rejection, and cleaning efficiency. Experiments were carried out at three levels of sieve slopes (5, 10, and 15°), two sieve reciprocating speeds (0.48 and 0.95 m·s−1), two levels of feed rates (1 and 1.5 kg·min−1), and three air velocities (5, 6 and 7 m·s−1). The results showed that, at sieve reciprocating speed of 0.95 m·s−1, the maximum cleanliness value was – 96.25% – observed at 1.5 kg·min−1 feed rate, 5 m·s−1 air velocity and 5° sieve slope. The minimum cleanliness value – 76.82% – was observed at a feed rate of 1 kg·min−1, 15° sieve slope, 7 m·s−1 air velocity, and 0.48 m·s−1 sieve reciprocating speed. The results showed that the use of either a very low, or a very high sieve slope angle and sieve reciprocating speed while using different air velocities and feed rates is not recommended.

Combining stratigraphic forward modeling and susceptibility mapping to investigate the origin and evolution of submarine canyons

The debate on the submarine canyon origin between the upslope erosion model dominated by retrogressive mass failures and the downslope erosion model controlled by gravity flows has not been fully settled. However, this debate is critical for explaining submarine canyon evolution. This study combines susceptibility mapping and stratigraphic forward modeling (SFM) to examine the origin and evolution of submarine canyons under various fluvial discharge and morphologies. The SFM work consists of dozens of hypothetical numerical experiments based on typical passive margin bathymetry with half bathymetry occupied by an incipient canyon and associated river mouth topography, and another half bathymetry by steep slopes without canyons. Evolution characteristics in both plan and cross-section views are analyzed, and the impacts of fluvial and morphological features on canyon evolution are tested.The results indicate that the submarine canyons retreat landward, tributaries develop on the canyon outer banks, and blind canyons grow landward to capture small gullies and form shelf-incising canyons. The upslope pattern is dominant regardless of changes in fluvial discharge and morphologies. The locations of tiny gullies on steep slopes determine the distribution and growth direction of submarine canyons, whereas fluvial conditions and morphology parameters affect the canyon dimensions. High fluvial discharge and high canyon sidewall slope angle promote tributary development and canyon erosion. High canyon sinuosity leads to an asymmetrical distribution of tributaries on canyon outer banks whereas high regional slope angle increases the canyon length and decreases the canyon spacing.This study settles the debate between the upslope and downslope erosion models. In addition, it refines the upslope model by highlighting the importance of small-scale gullies and testing the influence of fluvial and morphological conditions on canyon evolution. The conclusions could promote the understanding of submarine canyons and assist in reservoir exploration and hazards prevention.

Seismic radiation analyses in anisotropic media based on general dislocation source model

AbstractAnisotropy affects the focal mechanism and makes it complicated. A shear motion generates a pure double-couple (DC) source in isotropic media. While in anisotropic media, it will produce non-DC components, which contain isotropic (ISO) and compensated linear vector dipole (CLVD) components. Besides, coupled with the diversity of fault motion, the source may become extremely complicated. In this paper, the seismic moment tensor is obtained based on the dislocation model, and then a variety of analyses are performed with the moment tensor, including moment tensor decomposition, radiation pattern, radiated energy ratio and seismic propagation characteristics. Since the anisotropy of the medium also influences seismic wave propagation, a hypothesis is made that the source region is minimal and anisotropic, but the propagation path is isotropic. The research gives some interesting conclusions. It is found that the anisotropy mainly affects the focal mechanism under low slope angle while high slope angle has little effect on the polarity. In terms of the moment tensor decomposition, if only one of ISO or CLVD exists, it can be asserted that the source region is anisotropic because ISO components are accompanied by CLVD components in isotropy media. As for the DC component, the results indicate it is one of the most important factors for determining the ratio of radiant energy. This paper presents some valuable findings of the focal mechanism of the general dislocation source under anisotropy, which helps to recognise the source characteristics of the earthquake and build solid foundations for the subsequent inversion of the focal mechanism.

Gully slope distribution characteristics and stability analysis for soil erosion risk ranking in parts of southeastern Nigeria: a case study

Critical slope stability analysis has proven to be a reliable technique which could be used in gully erosion risk assessments. The integration of experimental and stability modelling has assisted extensively in the analysis of natural slopes. In the current paper, several geotechnical properties and slope parameters were studied in an attempt to characterize gullying processes and risk in southern Anambra State, Nigeria. Field mapping, geotechnical analyses, geostatistical analyses, and limit equilibrium simulations were integrated to achieve the research objectives. The field measurements showed that most of the gullies are characterized by high slope angles ranging between 18° and 85°. Based on the geotechnical analysis, the soil slopes were observed to be highly vulnerable to landsliding. Principal component and regression analyses efficiently captured the interrelationships between the analyzed erosion gully parameters. Several slope stability models were used to estimate the factor of safety (FS) of the slope materials. It was revealed that most of the slopes are unstable and vulnerable whereas others are critically to moderately stable. Furthermore, while the slopes recorded FS in the range of 0.82–1.72 in unsaturated condition, FS of 0.70–1.33 was observed for saturated condition. This result indicated that the gully slopes are more vulnerable to failure by erosive forces in wet season, due to rainwater infiltration and pore-water pressure buildup. Gully slopes within the Nanka Formation showed higher failure vulnerability than those in Ogwashi and Benin formations. The details of this study would be helpful towards the mitigation of landslide hazards in the study area.

Effect of Parameters on the Runoff Erosion Control Performance of Structurally Modified Jute and Coir Geomeshes over Loamy Sand

Soil erosion is a serious environmental problem that can be controlled using bioengineering techniques. In using a bioengineering technique, temporary reinforcement is performed with geomeshes until vegetation takes root. In this study, structurally modified jute and coir geomeshes were tested for runoff erosion control and runoff volume over loamy sand at different slope angles. The laboratory results revealed that all parameters (slope angle, type of weave and type of material) had a significant effect on the erosion control performance of geomeshes. The slope angle contributed most (52.34%) to runoff erosion control, followed by weave type (25.79%) and type of material (12.28%). At lower and medium slope angles (of 15o and 30o, respectively) the twill-woven structure of coir geomeshes provided better erosion control than plain- and satin-woven structures, while plain-woven jute geomeshes demonstrated better erosion control at all slope angles. To understand the overall impact, a germination test was also conducted. According to the germination test results, the twill weave of jute geomeshes provided the highest rooting length. In general, plain-woven jute geomeshes are preferred for better erosion control on a high slope angle, while plain and twill can be used on a low slope angle.

Ecological preservation based multi-objective optimization of coastal seawall engineering structures

Intensive coastal reclamation activities can lead to ecological degeneration in coastal areas. Therefore, the engineering design concept of an ecosystem-based coastal reclamation has aroused great interest. However, the inconsistency of standards and the unclear understanding of ecological processes are the difficulties in this field. In this paper, we selected eco-seawall as object to determine and optimize the 4 engineering parameters (including L1, L2, a, and h1). We set up 20 groups of working conditions under analyzing, and applying a computational framework to optimize eco-seawall designing processes. The computational efficiency would be enhanced by this developed method from the following aspects: (a) establishing surrogate model for eco-seawall to replace the high cost of simulation process; (b) searching engineering control parameters to optimize eco-seawall design; (c) obtaining the Petro curve set of optimal parameters for coastal reclamation management and ecological restoration. The design domain of the related parameters was determined by analyzing simulated and experimental data. As the results, the design domain were obviously reduced through optimization process: L1∈[0.1, 0.3]; L2∈[0.2, 0.8]; a∈(30,60]; h1∈[0.2,0.4]. Additionally, according to pilot-scale experiment, it can be concluded that the overtopping frequency for the low slope angle dam is 66.7%; the overtopping frequency for the high slope angle dam is 44.4%. The optimal design range for the practical engineering design can be provided by the optimal solution set of eco-seawall obtained from the optimization results. The calculation approach used in this research will provide reference for other engineering optimization work.

Large‐scale land acquisition as a potential driver of slope instability

AbstractRecently, vast tracts of land have been acquired by foreign and domestic–foreign partnerships to satisfy an increasing demand for agricultural products, often resulting in the conversion of forested landscapes into agricultural fields. Those conversions often occur in areas characterized by high slope angles with the potential to cause mass wasting and shallow landslides. An interesting case‐study is the Licungo basin in Mozambique, where from 2000 nearly 160,000 ha of forest were converted, 17% of which occurred in areas acquired through large‐scale land acquisitions (LSLAs). This study analyses the relationship between deforestation occurring within LSLA areas and the likelihood of landslide occurrence. To this end, we use a spatially distributed physically based model that couples the assessment of slope stability with hillslope‐scale hydrological processes and evaluates the change in slope stability associated with remotely sensed forest loss. Relative to conditions where no human modification of land cover has occurred, we find that LSLAs have the potential to increase the extent of areas susceptible to slope failure by as much as 15,000 ha. We also quantified potential direct and indirect implications of such events for the food supply of local populations, estimating that 4,000 people could lose approximately 700 kcal cap−1 d−1 if all LSLAs are put under production. This study demonstrates the linkages between LSLAs, slope instability, and knock‐on environmental and societal impacts. Governments should therefore take such impacts into account (in addition to those related to habitat destruction and carbon emissions) when issuing permits and concessions within forested lands.

Study on High and Steep Slope Stability and Slope Angle Optimization of Open-Pit Based on Limit Equilibrium and Numerical Simulation

The stability of open-pit slope is related to mine safety, especially for high and steep slope. In order to obtain the design slope stability and slope angle optimization of K mine open-pit in Myanmar, limit equilibrium analysis method and three-dimensional numerical simulation are used to carry out the study on the slope stability. The results show that: (1) The safety factor of the designed slope is larger than the allowable safety factor by using the limit equilibrium analysis, which belongs to the stable slope. Some areas can be optimized for design. (2) Through three-dimensional numerical analysis, the design slope and the optimized slope are both stable. The area with large deformation of the optimized slope is mainly concentrated in the area of 562 m level moderately weathered pyroclastic rock in area A and 560 m level moderately weathered rock in area B. The calculation results of three-dimensional numerical simulation are basically consistent with the results of the limit equilibrium analysis. (3) Compared with the designed slope, the potential sliding surface position of the optimized slope is lower. The safety factor is smaller, but larger than the allowable safety factor. The shape of the sliding surface of the whole slope is nearly circular arc. The sliding mode of the slope is circular arc sliding. (4) The reasonable slope angle of different engineering geological divisions of the open-pit slope of K mine is determined. The overall slope angle of area A is ≤ 46°. The overall slope angle of area B is ≤ 44°. The overall slope angle of area C is ≤ 45°. The overall slope angle of area D is ≤ 50°. The research results can provide reference for mine safety production.

Evaluation of a reservoir landslide: a case study from Artvin, Turkey

This paper describes an instability in the Yokuslubag village of the Yusufeli district of Artvin in Northeastern Turkey. The Arkun Dam was one of the dams planned on the basin of the Coruh River. The Yokuslubag landslide area starting at 600 m upstream is on the left side of the Arkun Dam. The sliding area is approximately 2 km2. The landslide consists of rockfalls, rotation slides, planar slides, slope wash deposit and alluvial fans. The causes of the slidings are the toe erosion by the Coruh River, high slope angles varying between 20° and 35°, rockfalls in the Berta Formation and hydrothermal and physical weathering. Lithology boundaries and possible sliding surfaces were determined with drilling and resistivity studies. One hundred iron bars were fixed on the landslide, and the movements of these iron bars were recorded. The Yokuslubag landslide was determined as a huge creep. Two possible sliding surfaces were determined. When the water was accumulated in the reservoir, the toe of landslide would be under reservoir lake. This would increase landslide velocity and may cause dam failure. According to the first possible sliding surface, the sliding material amount was calculated as approximately 100 × 106 m3. This material would fill approximately 1/3 of the reservoir of the Dam. If the second possible sliding surface mobilized, approximately 130 × 106 m3 of material would move into the reservoir. According to these possibilities, the Arkun Dam project was canceled, and other alternatives were considered.

Effect of slope angle on muscle activity during variations of the Nordic exercise.

This study investigated the muscular activity of the lower muscles during variation of Nordic exercises following changes of the Nordic angles and the base slope angles. Twenty-one healthy participants were participated in this study. Participants performed six variations of Nordic exercises including two Nordic angles positions and three base slope angles. Each Nordic exercise defined as Nordic angle 10°, 15° and base slope angle 0°, 10°, 15°. During the Nordic exercises, erector spine, gluteus maximus, biceps femoris, gastrocnemius activities and subjective difficulties (Borg RPE score) were measured. The activities of all muscles and subjective difficulties were significantly greater with the 15° of Nordic exercise compared to the 10° of Nordic exercise, regardless of base slope angles. There were significant differences in gluteus maximus, biceps femoris, gastrocnemius, and the Borg RPE score between three base slope conditions (P<0.05). The Borg RPE score and activities of the gluteus maximus were increased with the increases of base slop angles from 0° to 15°. Conversely, the activities of the gastrocnemius and biceps femoris were decreased with the increases of base slop angles from 0° to 15°. Present study indicates that application of the greater Nordic angle during the Nordic exercise is advantageous for activating lower extremity muscles. Using the base slopes during the Nordic exercise could be used for selective activation of the lower muscles. High base slope angles inducing greater knee flexion could maximize the exercise effects for activating gluteal muscles rather than lower leg muscles such as biceps femoris and gastrocnemius.

Anatomical Differences Between Foot and Hand Web Space Reconstruction

The differences in the anatomy of the foot and the hand may affect the dorsal flap design for web space reconstruction. In this study, the authors aimed to identify the differences in web space anatomy of the foot and the hand and provide a guideline of flap design for web space reconstruction in the foot and the hand. The right hands and right feet of adult volunteers were measured, including surgical landmarks (i.e., the dorsal prominence of proximal interphalangeal and metacarpophalangeal joints [or metatarsophalangeal joints]), proximal phalangeal length, tip of the web space, and width of web space. The web spaces and other parameters were analyzed and compared between the foot and the hand by using a paired t test with p < .05 to indicate statistical significance. A total of 108 web spaces of the foot and hand from 18 adult volunteers were analyzed. The parameters that were significantly different between the foot and the hand included (1) proximal phalangeal length (34.63 vs 60.16 mm), (2) average web height ratio (0.72 vs 0.51), (3) average web width ratio (0.69 vs 0.81), (4) mean slope angle (4.89° vs 19.26°), and (5) average abduction angle (25.33° vs 31.07°). In conclusion, the foot web space had a higher slope angle, less abduction angle, and shorter proximal phalangeal length. Therefore, the flap design for foot web space reconstruction requires a longer and narrower flap than the design for the hand. The recommended flap design length should be at least 72% of proximal phalangeal length for the foot versus 51% for the hand, and the width should be at least 69% of the distance between the tips of adjacent metatarsophalangeal joints for the foot versus 81% for the hand.

Geotechnical properties and stability of the submarine canyon in the northern South China Sea

The upper part of the continental slope in the northern South China Sea is prone to submarine landslide disasters, especially in submarine canyons. This work studies borehole sediments, discusses geotechnical properties of sediments, and evaluates sediment stability in the study area. The results show that sediment shear strength increases with increasing depth, with good linear correlation. Variations in shear strength of sediments with burial depth have a significantly greater rate of change in the canyon head and middle part than those in the canyon bottom. For sediments at the same burial depth, shear strength gradually increased and then decreased from the head to the bottom of the canyon, and has no obvious correlation with the slope angle of the sampling site. Under static conditions, the critical equilibrium slope angle of the sediments in the middle part of the canyon is 10° to 12°, and the critical slope angle in the head and the bottom of the canyon is 7°. The results indicate that potential landslide hazard areas are mainly distributed in distinct spots or narrow strips on the canyon walls where there are high slope angles.