Height Distribution Curve Research Articles

Analysis of Selection-Cutting Silviculture with Thujopsis dolabrata—A Case Study from Japan Compared to German Plenter Forests

(1) Background: In Japan, single-tree selection-cutting silviculture with hiba (Thujopsis dolabrata var. hondai) is a traditional silvicultural system and is well documented. We evaluated an experimental forest regarding past structural dynamics and future development while comparing it to the German multilayer coniferous “Plenterwald/plenter forest”. (2) Methods: Classical growth and yield data were recorded since 1995 from two hiba-mixed species plots, one managed since Matsukawa’s (the founder) times in 1931 and the other unmanaged since 40–50 years before 1931. (3) Results: Clear structural differences appeared, with the managed plot having a reverse J-shaped DBH and tree height distribution curve, and a higher percentage of hiba, also typical for German plenter forests’ intensely multi-storied structure. The unmanaged plot was composed of trees with large stem diameters, even though they were more evenly distributed, together with less admixed species. In both plots, the growing stock increased in the past. While the managed plot’s growing stock in 2019 was 561 m3 ha−1, the unmanaged plot reached 982 m3 ha−1 with large portions accumulated in DBH classes >60 cm. (4) Conclusions: When compared to today’s clearcutting system in Japan, selection silviculture shows advantages and may thus serve as a valuable inspiration for silviculture in Japan as it was with plenter forestry for Germany.

Wave Hydrodynamics across Steep Platform Reefs: A Laboratory Study

This paper presents a laboratory study on wave transmission across steep platform reefs, aiming at furthering knowledge of wave hydrodynamics and establishing empirical formulations of spectral wave parameters across the reef flat. The ultimate aim of this study is to determine the design wave load to design fixed offshore structures on coral reefs flat. The process of wave transmission across the underground coral strip with a large front slope has been studied on a physical model in the wave trough with nearly 300 experimental cases combined from 05 underground band models and many random wave scenarios and scenarios at different submerged depths. Experimental results show that the abrupt transition in depth from deep water ahead to relatively shallow water in the reef is responsible for the difference in the wave at the top of the strip compared to the wave on the normal beach, especially regarding the statistical distribution of the wave height. Breaking waves at the abrupt transition have deviated the wave height distribution curve from the deep-water (Rayleigh) theoretical distributions and even the existing shallow-water distributions, including the effect of breaking waves. Two sets of empirical formulations of the spectral wave parameters (Hm0 and Tm-1, 0) are eventually derived for the surf zone and the region behind the surf zone, respectively. These local wave parameters can be used as inputs to a wave height distribution model for determining other design characteristic wave heights on steep platform reefs. Doi: 10.28991/CEJ-2022-08-08-015 Full Text: PDF

Topographic evolution of balls used in microabrasion tests

This work aims to contribute to the understanding of the topographic modification of the surface of the counter-body during micro-abrasion and its complex relationship with specimen wear. The topographic evolution of the surface of five different balls (Ø25.4 mm) was monitored: one ceramic (Si3N4), one metal (AISI 52100 steel), and three thermoplastic polymers (polypropylene, polyacetal and polyamide 6.6). AISI 304 austenitic stainless steel specimens were tested in a fixed-ball micro-abrasion test rig using a silica slurry (10%wt. in water), rotation speed of 150 rpm, and total test time of 90 min (in 15 min intervals). The topographic evolution of the ball topography was monitored by laser interferometry of the abrasive tracks at each measurement interval, always in the same region. The parameters Sq, Sz, Ssk, Sku, λq, Sdq and Str were computed. Significant wear and changes of the surface topography of the balls were observed along the tests. Harder balls underwent evident grooving, while the softer polymeric balls showed fibrillation characteristics, alignment of polymeric chains and transfer film. For the initial 15 min of test, before reaching a steady-state wear regime, the softer balls (polypropylene, polyamide 6.6 and polyacetal) showed, in general, an increase in Sq, λq and Sdq, possibly by the generation of a transfer film on the surface, which was not observed for the harder balls. After the steady-state regime was achieved, all balls reduced their values of Sq, λq and Sdq. Plots of Sku x Ssk identified non-Gaussian height distribution curves (mostly with high kurtosis and negative asymmetry) for all balls. Sq and Sdq presented a linear relationship with the wear coefficients of the specimens (k) dependent on the material of the ball, whereas an overall linear relationship between λq and k was observed independently of the ball material. Str was a good indicator of aligned grooving abrasion, but showed a linear relationship with k only for the steel ball.

Multi-wavelength light-emitting diode light source radar system and near-ground atmospheric aerosol detection

Near-ground atmospheric aerosol has a direct effect on the living and production of human, and the research on its detection attracts substantial attention from engineers and scholars in the community of environment. Traditional monitoring instruments can accurately and continuously detect the aerosols above the ground, but it is difficult for them to obtain the information about vertical distribution of near-ground aerosols. As is well known, lidar can act as an efficient method to detect the aerosol's temporal and spatial distribution. However, this technique is restricted in the potential applications of the detection of aerosol at a certain wavelengths or near range. That is because it usually presents fixed wavelengths and a large blind area. In this work, a new multi-wavelength light-emitting diode (LED) light source radar system is designed and established for detecting the characteristics of atmospheric aerosol near ground. The paper is outlined as follows. Firstly, the composition and working principle of the LED light source radar system are introduced. Based on the structure of radar's transmitter and receiver, the geometric overlap factor is analyzed and calculated. The minimum detection height of the LED light source radar system is then determined to be 60 m. Secondly, the inversion method for the echo signal of LED light source radar is studied. In consideration of the suitability of near-range detection of LED light source radar, the Fernald forward integration method is used for inversing the aerosol extinction coefficient. The calibration value of aerosol extinction coefficient is further determined with the ground visibility data. Finally, by using the designed multi-wavelength LED light source radar system (475 nm, 530 nm, and 625 nm), near-ground aerosol observation at night in Xi'an city is carried out and three atmospheric conditions including light, moderate and severe pollution days are considered. The height distribution curves of atmospheric aerosol extinction coefficient of three wavelengths within a height of nearly 300 m are obtained. The characteristics of the distribution and change of near ground aerosols are accordingly discussed. The experimental results show that the multi-wavelength LED light source radar provides an efficient implementation for detecting the vertical distribution of atmospheric aerosol near the ground, and can make up for the inadequacy of lidar in near range detection.

HYPSOMETRY OF THE LARGEST OCEANIC ISLANDS

Digital database and theoretical height distribution curve obtained from energetic model were used for hypsometric analysis. The possibilities of this approach are discussed.

INVESTIGATING SILVICULTURAL CHARACTERISTICS OF YEW (TAXUS BACCATA L.) STAND USING FULL-CALLIPERING IN NORTHERN FORESTS OF IRAN

In this research, some of site and silvicultural characteristics of Yew stand in northern forests of Iran was studied. For this purpose, compartment number 16 of district 4 Shir-ghalaye was selected. According to research purposes, stands with an area of 20 ha were chosen in center of the compartment and was separated from map. Due to restricted area of region and according to few number of Yew trees in the stand, the full-callipering method was conducted for measuring quantitative and qualitative characteristics. In the stand diameter at breast height (D.B.H.), height and canopy diameter of all Yew trees were measured. The results showed that the diameter distribution curve and height distribution curve of Yew trees were similar to even-age forests curve. But according to average annual increment, mixture type of Yew trees in stand, diameter distribution of other species and low rate regeneration of Yew, it can be concluded that the studied Yew stand, is an uneven-age stand and because of low rate regeneration in previous years the number of young Yew trees were reduced and even-age forest curve was formed subsequently. The maximum height and diameter of Yew trees were recorded 26.8 m and 112 cm, respectively. Also, the number of trees per hectare and basal area per hectare of Yew trees were calculated 14.55 and 3.23 m2 respectively.

微通道板光子计数成像探测器预处理实验研究

A preconditioning process encompassed vacuum baking and burn-in with ultraviolet radiation.An equipment of preconditioning of microchannel plate was designed which could provide vacuum environment(10-5 Pa at least) as well as heating elements.The heating elements were controlled to reach 350℃ and then the vacuum chamber was sustained 350℃ for 18 hours in the procedure of bake-out.The burn-in procedure illuminating with ultraviolet radiation(253.7 nm) from a deuterium lamp was achieved when 0.06 Coulomb cm-2 was extracted from the MCP stack output.After the preconditioning the image spatial resolution reached to 125 μm,the background events rate dropped to be 0.53 counts/s·cm2 from 27.09 counts/s·cm2,the pluse height distribution curve closed to Gauss distribution and turned to be more narrow.

Determination of aeolian transport rates of volcanic soils in Iceland

Sandy deserts cover >20000km2 in Iceland, consisting primarily of volcanic materials with basaltic volcanic glass being the main constituent. Wind erosion is severe in the country, causing dust pollution with widespread aeolian redistribution affecting most Icelandic ecosystems and sand movement over vegetated areas in the form of advancing sand fronts. We quantified wind erosion, using BSNE field samplers and automated sensors over several years at two sites with contrasting environments. The study sites are Holsfjöll with andic soil materials in the arid northeast highlands (<400mm annual precipitation) and Geitasandur on sandy surfaces in the humid south lowlands (>1200mm). Both areas show similar annual aeolian transport of 120–>670kgm−1yr−1. Aeolian flux in storms at the NE site was 3–43kgm−1h−1 on average with up to >200kgm−1h−1 during gusts. Multiple regression shows potential flux of >200kgm−1h−1 during intense storms of >20ms−1 (at 2m height). The research shows major aeolian activity in the humid South Iceland. Height distribution curves indicate considerable transport high above the surface at both sites (>60cm). Stable height distribution curves for each location allow for measurements using single dust trap over long periods. The research explains the intense activity of advancing sand fronts in Iceland and the significance of continuously recharged sand sources for maintaining severe wind erosion in humid areas of Iceland.

Influence of contact pressure and boundary films on the frictional behaviour and on the roughness changes of galvanized steel sheets

This paper tackles the effects of contact pressure and of an industrial surface chemical treatment, which is called New Inorganic Treatment (NIT), on the frictional behaviour and the roughness changes of hot-dip galvanized mild steel sheets. Samples of different topographies are investigated by plane friction test with increasing contact pressure and 3D profilometry.For non-chemically treated (non-NIT) surfaces, friction coefficient is an increasing function of pressure. Moreover, above a certain pressure, which seems to depend on topography, a stick-slip phenomenon occurs. For chemically treated (NIT) surfaces, no stick-slip phenomenon is observed. Friction coefficient is lower than for non-NIT surfaces and, above a certain pressure, decreases as pressure increases. The behaviours of the 4 morphological textures investigated, either electron beam textured (EBT) or electron discharge textured (EDT), are qualitatively identical.The roughness is a decreasing function of pressure except during stick-slip phase, during which roughness evolves erratically at values higher than what the imposed pressure should lead to. The observation of height distribution curves reveals the very different surface deformations between non-NIT and NIT surfaces, whatever the topography. We conclude that, by reducing local friction shear stress, an indirect effect of the chemical treatment is the modification of the deformation mode of zinc asperities, which in fine would reduce the amount of wear debris.

Properties of photon counting imaging system with Si thin films

The Si thin films on ceramic substrates,which were fabricated by electron beam evaporation,were applied as charge induction layers in photon counting imaging system with induction readout. The structures and micrograph of Si thin films were studied. The X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM) images indicate that the thin film has amorphous structure and is coarse due to the lattice boundary of ceramic substrate. The experimental setup was established and the detector resolution,counting rate,pulse height distribution curves etc., with different Si film thickness were compared. The results suggest that the film thickness influences on spatial resolution less than on the counting rate. Moreover,the properties of the system with Si and Ge thin films of the same resistance were compared,which shows that the properties such as distortion,counting rate and dark count rate are better with the Si films.

Effect of Surface Pattern on Stribeck Curve

The effect of surface pattern on frictional characteristics of lubricated contact is studied. An algorithm based on the load-sharing concept is developed which assumes that the total transmitted load is carried by the asperities as well as the fluid film. Surface roughness for specified values of surface pattern number is generated assuming a Gaussian height distribution and Stribeck-type curves are obtained for isotropic, transverse, and longitudinal surfaces. The predictions of the model are verified by comparing published results on non-conformal contact of rollers and also a heavily loaded, conformal pin-bushing assembly. The results reveal that surfaces with transverse pattern generate larger friction than those with longitudinal surfaces. Transverse surfaces perform a higher film-forming capacity compared to isotropic and longitudinal surfaces.

An ultraviolet photon counting imaging detector system based on Ge induction readout mode

Photon counting imaging technology has been widely used in nuclear radiation detection, space environment detection, astronomy observation, nuclear physics and ultraweak bioluminescence. The structure and operating principles of ultraviolet photon counting imaging systems based on direct electron collection mode and induction readout mode are introduced, but there are more advantages with the induction readout mode. The gain characteristic, resolution, linearity and count rate of a system based on induction mode are evaluated. The dark count pulse height distribution curves shift towards higher pulse height, and the dark count rate increases as the voltage increases. The pulse height distribution curves with light incidence also indicate that the count rate with higher pulse height increases as the voltage increases. The resolution test results show that the system resolution is better than 100 μm along the Y direction and better than 80 μm in some areas. The nonlinearity in both directions is less than 5% in a Φ35 mm area. The system resolution at a low count rate is better than that at a high count rate.

Protein Immobilization on Epoxy-Activated Thin Polymer Films: Effect of Surface Wettability and Enzyme Loading

A series of epoxy-activated polymer films composed of poly(glycidyl methacrylate/butyl methacrylate/hydroxyethyl methacrylate) were prepared. Variation in comonomer composition allowed exploration of relationships between surface wettability and Candida antartica lipase B (CALB) binding to surfaces. By changing solvents and polymer concentrations, suitable conditions were developed for preparation by spin-coating of uniform thin films. Film roughness determined by AFM after incubation in PBS buffer for 2 days was less than 1 nm. The occurrence of single CALB molecules and CALB aggregates at surfaces was determined by AFM imaging and measurements of volume. Absolute numbers of protein monomers and multimers at surfaces were used to determine values of CALB specific activity. Increased film wettability, as the water contact angle of films increased from 420 to 550, resulted in a decreased total number of immobilized CALB molecules. With further increases in the water contact angle of films from 55 degrees to 63 degrees, there was an increased tendency of CALB molecules to form aggregates on surfaces. On all flat surfaces, two height populations, differing by more than 30%, were observed from height distribution curves. They are attributed to changes in protein conformation and/or orientation caused by protein-surface and protein-protein interactions. The fraction of molecules in these populations changed as a function of film water contact angle. The enzyme activity of immobilized films was determined by measuring CALB-catalyzed hydrolysis of p-nitrophenyl butyrate. Total enzyme specific activity decreased by decreasing film hydrophobicity.

Relationship between the surface morphology and the height distribution curve in thermal evaporated Au thin films

We present the formal deduction of an analytic expression for the height distribution curves of scanning tunneling microscopy (STM) images obtained from Au polycrystalline thin films with a wide range of thicknesses (60–1800 nm). That expression is a function of statistical parameters measured from the minimalist surface elements of the images and can be employed when these parameters satisfy several statistical conditions. We show that the required experimental parameters fulfil these conditions in a reasonable way and we present the numerical synthesis of experimental height distribution curves. The interface width calculated from the synthesized curves is compared with the root mean square height of the images, and as a consequence the ≈1/3 scaling exponent is confirmed and the complex origin of the interface width in a competitive columnar growth is shown. The description of the minimalist parameters set is completed with two facts: all they present a similar scaling exponent and, following the deduced expression, the experimental height distribution curves collapse in a unique distribution curve for all the thicknesses. Several parameters are proposed as a clear alternative to the usual interface width and to the morphologic slope.

Surface protrusion parameters in film columnar growth

In order to unfold the components of the interface width w of a columnar growth we measured by scanning tunneling microscopy the parameters that define the surface-protrusion SP shapes and their fluctuations in the paradigmatic Au thin film growth. The profiles of SP sections can be fitted by parabolas y =abx 2 . The scaling of the shape mean parameters as well as their fluctuations is obtained. These parameters allow the synthesis of the height distribution curve, as well as the separation of the columnar height fluctuations at the surface. The mean value of the slope at the paraboloid section borders is maintained constant during the growth. An unstable growth model of terrace surface currents with a selected slope that includes a steering effect at the step borders allows interpreting this border slope property and its value. The scaling exponents of the interface width, coarsening, and shape parameters agree with the values obtained from solid-on-solid simulations by other authors. of the parameters with a growth model. Specifically, this growth model is based on a system of terrace surface cur- rents controlled by a high Ehrlich-Schwoebel ES barrier and descending mechanisms that include a combination of knockout and steering processes. We also discuss a possible detachment mechanism driven by a chemical surface poten- tial. Finally, the cause of the faceting of the thicker films is analyzed.

Digital generation of surface of asymmetrical height distribution

The paper presents digitally created 3D model of metal surface. The model possesses characteristic features of honed surface. Surface intersections are of plateau type. In addition, on level of mean ordinate value z= f( x, y) fractal structure was imposed on the surface. Abbot-Firestone Pmr(c) and height distribution curves z( x) in 2D (according to ISO 4287–1998) and 3D systems were analysed.

Analysis of cold rolled steels of different reduction ratio using the magnetic Barkhausen noise technique

Magnetic Barkhausen Noise (MBN) was used to evaluate the magnetic behaviour of nuclear reactor pressure vessel steel specimens cold rolled to reduction ratios between 0% and 60%. Measurements performed at increasing reduction ratios revealed variations in the angular dependence of a parameter termed ‘MBNenergy’, concurrent with modifications in the shape of the pulse height distribution curves. The angular preference of MBNenergy present prior to cold rolling was destroyed at intermediate reduction ratios (≈25%), and restored with further reduction (≈40%). Along the rolling direction, the number of large voltage pulses was reduced at reduction ratios of ≈25%, increasing again at ≈60% reduction ratio. Results were attributed to competing effects between crystallographic texture, microscopic and macroscopic residual stresses.

Experimental Investigation of Thermal Contact Conductance: Variations of Surface Microhardness and Roughness

Surface roughness parameters were measured using nine different sampling intervals. The results showed that the roughness of profile was nearly a constant at all sampling intervals; the slope, peak curvature and density of the profile decreased with increasing sampling interval; and the distribution of the peak height was different from the profile height distribution and was not Gaussian. It was found that the surface microhardness value, under small loads, varied with the indentation size and the surface preparation procedure. A model was developed which used a discretization method to obtain the contact radius and area in each section of the surface summit height distribution curve. This model eliminated some of the assumptions made by previous models and can be used to predict the thermal contact conductance without assuming the asperity deformation mode and surface summit height distribution. The predicted thermal contact conductance values were in good agreement with experimental results.

Early post‐fire regeneration of a Pinus halepensis forest on Mount Párnis, Greece

Abstract. The post‐fire regeneration of a 45‐yr‐old Pinus halepensis (Aleppo pine) forest, burned in July 1989, has been studied on Mount Párnis, Attiki, Greece. Four experimental plots at various slopes and exposures were established at altitudes of 400 ‐ 450 m, and monitored for 3 yr at 3‐month intervals. Early regeneration took place abundantly, through both resprouting and seed germination of mostly hard‐seeded herbs and shrubs; the floristic richness was high with 80 taxa. Pine seedling emergence took place during the winter of the first post‐fire year. The mean pine seedling density by the end of the recruitment period (March 1990) was 5–6 seedlings/m2. This density decreased slightly during late spring and considerably during summer. During the second post‐fire year only a relatively slight decline was observed; thereafter the density was stabilized to 1 ‐ 2 seedlings/m2. Mortality follows a negative exponential curve that levels off at ca. 20 %. Height distributions throughout the three post‐fire years were all positively skewed as a result of the presence of few very tall saplings. A considerable fraction (20 %) of very short (5–15 cm) saplings were still alive 39 months after the fire; these may constitute the sapling bank. Based on the analysis of height distribution curves, it is concluded that the taller seedlings survived significantly better than the shorter ones.

A New Quantitative Roughness Measurement and its Application in the Polysilicon/Silicon Dioxide Interface

ABSTRACTA quantitative approach for characterizing the interface roughness between two materials by cross sectional transmission electron microscopy (XTEM) is proposed. This approach is based on obtaining an interface height distribution curve (IHDC). The interface roughness can be characterized quantitatively by extracting from IHDC three parameters: the mean, median and maximum interface height. This new method has been applied in the characterization of the interface between thermally grown silicon dioxide and polycrystalline silicon thin films deposited by low pressure chemical vapor deposition. It is shown that high temperature processing yields an interface that has higher roughness.