Влияние условий осаждения из паров металлоорганических соединений на получение эпитаксиальных слоев n-CdTe с использованием изопропилиодида

The dependence of iodine incorporation in CdTe layers on the deposition conditions during metalorganic vapor phase epitaxy is investigated. The growth of the layers was carried out from dimethylcadmium and diethyltellurium in the hydrogen flow in a vertical reactor with a hot wall condition at a total pressure of 20 kPa. The total iodine concentration was determined by secondary ion mass spectrometry, the electrically active concentration was determined from the Hall effect measurement. The iodine incorporation depends on the crystallographic orientation of the substrate (were studied (100), (310), (111)A, (111)B, (211)A and (211)B), the concentration of the doping precursor (flux range 5·10–8–3·10–6 mol/min), the mole ratio of organometallic compounds (DMCd/DETe=0.25–4), growth temperature (335–390°C) and the walls of the reactor above the pedestal (hot wall zone 290–320°C). The total iodine concentration reached 5·1018 cm–3 and the activation efficiency was ~4 %. After thermal annealing in cadmium vapor at 500°C the activation efficiency was ~100 %.

On the efficiency of coupled discrete-continuum modelling analyses of cemented materials

Computational load of discrete element modelling (DEM) simulations is known to increase with the number of particles. To improve the computational efficiency hybrid methods using continuous elements in the far-field, have been developed to decrease the number of discrete particles required for the model. In the present work, the performance of using such coupling methods is investigated. In particular, the coupled wall method, known as the “wall-zone” method when coupling DEM and the continuum Finite Differences Method (FDM) using the Itasca commercial codes PFC and FLAC respectively, is here analysed. To determine the accuracy and the efficiency of such a coupling approach, 3-point bending tests of cemented materials are simulated numerically. To validate the coupling accuracy first the elastic response of the beam is considered. The advantage of employing such a coupling method is then investigated by loading the beam until failure. Finally, comparing the results between DEM, DEM-FDM coupled and FDM models, the advantages and disadvantages of each method are outlined.

Ventilation and Pollutant Concentration for the Pedestrian Zone, the Near-Wall Zone, and the Canopy Layer at Urban Intersections

To gain further insight into the ventilation at urban street intersections, this study conducted 3D simulations of the ventilation at right- and oblique-angled intersections under eight wind directions by using the Reynolds-averaged Navier–Stokes (RANS) κ-ε turbulence model. The divergent responses of ventilation and pollution concentration for the pedestrian zone (ped), the near-wall zone (nwz), and the canopy layer to the change in intersection typology and wind direction were investigated. The flow characteristics of the intersections, taken as the air flow hub, were explored by employing indices such as the minimum flow ratio (β) between horizontal openings. The results show that oblique wind directions lead to a lower total volumetric flow rate (Qtotal) but a higher β value for right-angled intersections. For T-shaped intersections, a larger cross-sectional area for the outflow helps to increase Qtotal. Oblique-angled intersections, for example, the X-shaped intersection, experience a more significant difference in Qtotal but a steady value of β when the wind direction changes. The vertical air-exchange rate for the intersection was particularly significant when the wind directions were parallel to the street orientation or when there was no opening in the inflow direction. The spatially averaged normalized pollutant concentration and age of air (τ*¯) for the pedestrian zone and the canopy layer showed similar changing trends for most of the cases, while in some cases, only the τped*¯ or τnwz*¯ changed obviously. These findings reveal the impact mechanism of intersection configuration on urban local ventilation and pollutant diffusion.

Zoning Lubricant Die Application for Improving Formability of Box-Shaped Deep Drawn Parts

The ‘formability’ of sheet metal is a major keyword referring to process design in the sheet metal forming industry. Higher formability could reflect lower production costs and time. Many studies have been carried out to improve formability in various ways, by using the finite element method and experimental approaches. In the present research, a new zoning lubricant technique is proposed. The stainless steel SUS304 square deep drawn box is used as an investigative model. Based on the material flow analysis, we found that zoning lubricant die application could reduce the difference in material flow velocity between wall and corner zones. This material flow characteristic resulted in decreased nonconcurrent plastic deformation during the deep drawing process, as well as decreased stretching in the cup wall and the delaying of the fracture. In the present research, the design of the zoning lubricant die was strictly concerned with achieving functionality related to the friction coefficient, area of zoning, and blank-holder pressure. A smaller friction coefficient positioned in the corner zone and larger friction coefficient positioned in the wall zone are recommended. It was revealed that, by appropriate zoning lubricant die application, formability could be increased in terms of box height by approximately 7 mm or 10%.

CFD Analysis of Diverse Serrated Blade Configuration Effects on Fluid Flow of a Modified Centrifugal Fan

This paper presents the effects of the diverse serrated blade configurations on airflow characteristics of a modified centrifugal fan by CFD. This application is investigated to improve aerodynamic performance. These configurations (USB, ISB, USB, OSB) are simulated at the impeller speed levels by CFD. Then tested to analyze airflow characteristic values by ANCOVA test. The simulation results show that the BSB configuration achieves the high static pressures about 84.5-214.7 Pa in the wall zone. While the ISB generates the lower TKE in all the zones, except in the impeller zone. It produces about 0.51-12.47 m²s^-2 TKE in the wall zone. The ANCOVA test results indicate that the effects of the impeller speed are very significant (a < 0.01) on the airflow characteristics in all the zones, except for static pressure is no significant (a > 0.05) in the impeller and fluid flow zone. The effect of the serrated blade configurations is very significant on static pressure in the inlet and wall zone, and significant (a < 0.05) in the fluid flow zone. While it is very significant to air velocity in the impeller, fluid flow, and wall zone, and very significant on TKE in the impeller zone and outlet zone.

Pan-African rare metals bearing pegmatites in Wadi Ghadir, South Eastern desert, Egypt: the geochemical evolution and implications for mineralization

Quartz-diorites, monzogranites and pegmatites are the main rock units in the studied area. The pegmatites occur as zoned pockets within monzogranites with zonal arrangement: border, wall, intermediate, and core zones. The wall zone have enrichment of radioactive and RREs-bearing minerals. K-feldspar, plagioclase and quartz are essential minerals, whereas uranothorite, columbite, zircon, xenotime, monazite, sphalerite and pyrite are accessories. Geochemically, the pegmatites of W. Ghadir have peraluminous character, ferroan with alkalic–calcic affinity and emplaced in within plate setting. These pegmatites revealed Li-bearing variety and high level of rare earth elements mineralization. The studied pegmatites exhibit high contents of Li, Nb, Cu, Ta, U, Th, Pb, Zr, Zn and Ga, can be from the previous data, the studied pegmatites can be classified as a Niobium–Yttrium–Fluorine (NYF) pegmatite or rare metal pegmatite. The trace elements ratio supports a low degree of fractionation and metasomatism in the evolutionary history of the pegmatites, and the very low Cs values (2.2–4.3 ppm) indicate paucity of alkali metal fractionation. Spectrometric investigation revealed that monzogranites are not uraniferous, while the radioactive anomaly is confined to the pegmatites. Applying the U mobilization equation proved that pegmatite samples have been originated from a late magmatic phase of magma very rich in radioelements, and the pegmatites affected with hydrothermal solutions rich in uranium than thorium which indicates uranium addition. Radioactive and important heavy minerals are represented by uranothorite, columbite, zircon, monazite, xenotime, sphalerite and pyrite.

Evolution of the crystallisation conditions in the Wellington Lake Pegmatite in the Pikes Peak Granite, Colorado (USA)

<p>Pegmatites are texturally, mineralogically, and geochemically zoned rocks that show distinctive features such as graphic granite in the wall zones, coarse-crystalline material in the centre, and unusual mineralisation sometimes of economic significance. They are usually considered to be derived from silicate melts, but a significant fluid supply is also required to reproduce their unique characteristics. These fluids are commonly enriched in flux anions such as F<sup>-</sup>, Cl<sup>-</sup>, CO<sub>3</sub><sup>2-</sup>, and BO<sub>3</sub><sup>3- </sup>. Many studies have investigated the petrogenetic processes that led to pegmatite crystallisation, yet not all aspects of pegmatite formation have been fully understood. Notably, the nature of the precipitating medium remains uncertain for the different zones of the pegmatite. In order to better understand the transition from a silicate-melt-dominated crystallisation to fluid-dominated precipitation, we aimed to produce a temperature profile across the pegmatite and its host granite. We analysed quartz crystals from the different zones of the Wellington Lake Pegmatite and the host rock, a syenogranite of the Pikes Peak Batholith, in Colorado (USA). This NYF-type pegmatite consists of a fine-grained graphic granite wall zone, a coarse-grained quartz and albite intermediate zone, and pure blocky quartz core zone with REE-dominated mineralisation including fluocerite, bastnäsite, thorite, columbite, zircon, and cassiterite. Quartz trace element data (Al, Ti, Ge) suggest that the granite crystallized over a range of conditions, with Ti-in-quartz temperatures varying from 800 to 550°C. The wall zone of the pegmatite crystallised over a more constricted range, with temperatures on the order of ~660 to 630°C, just below the experimentally determined H<sub>2</sub>O-saturated haplogranite solidus. Finally, the intermediate and core zones of the pegmatite show much colder conditions, with fluid inclusion homogenisation temperatures calibrated for typical pegmatite pressures ranging from 450°C (for 300 MPa) or 380°C (for 200 MPa) for the intermediate zone to 380°C (for 300 MPa) or 325°C (for 200 MPa) for the core. These results suggest crystallisation from a range of conditions transitioning from hydrous silicate melt-based mineral precipitation at the high temperature end (in the core of quartz crystals in the granite) to sub-solidus Al-Si-Na-enriched fluid precipitation in the interstitial quartz of the granite and in the pegmatite. Textural and geochemical zoning in the pegmatite records the transition from near-magmatic conditions in the borders to colder and more hydrothermal conditions in the core.</p><p> </p>

Study of the causes for wax deposition under the operating conditions of main oil pipelines

The results of investigations of the main causes and the most significant factors of intensification of paraffin deposition in main oil pipelines are presented. A comprehensive analysis of the composition and properties of commercial oils and their sediments was carried out, according to which phase diagrams of equilibrium of oil dispersed systems were obtained using the example of commercial oils from Bashkir fields. Based on the phase diagrams, a curve of wax oil saturation was constructed, the analysis of which confirms that the existing thermobaric conditions during the operation of main oil pipelines do not allow transporting oil without the risk of waxing. It was noted a special influence of the value of the temperature gradient in the near-wall zone and the imbalance of the ratio of high-molecular oil components in commercial batches formed in the process of joint pumping on the intensity of waxing of sections of oil pipelines complicated by deposits, which was confirmed by statistical data on the frequency of pigging. The regularities obtained in this way are proposed to be used as an express method for predicting complications associated with intensive waxing of main oil pipelines. In order to quickly assess the risks of waxing of sections of main oil pipelines, an indicator is introduced that characterizes the ratio of the content of solid paraffins to the total content of resins and asphaltenes of oil, called the criterion of instability of a commercial oil batch.

Implementasi Pemantauan Suhu Kelembaban serta Pengendali Penyiraman Tanaman secara Otomatis pada Greenhouse Berbasis Web

AbstrakAglaonema merupakan tanaman hias daun yang memiliki nilai keindahan pada variasi daun, baik motif warna maupun bentuk daun. Aglaonema tumbuh pada suhu 24-270C dan kelembaban 65-75%, serta tidak terkena sinar matahari langsung. Untuk mendapatkan kondisi ideal maka aglaonema ditempatkan didalam sebuah greenhouse. Sehingga dirancanglah sebuah sistem yang dapat memantau suhu, kelembaban serta pengendalian penyiraman tanaman secara otomatis pada greenhouse. Adapun alat yang digunakan untuk merancang sistem ini adalah sensor DHT22, mikrokontroller Arduino uno, relay, selenoid valve, ethernet shield dan pompa air. Sensor ditempatkan pada 3 loakasi di dalam greenhouse yakni zona atap, zona dinding dan zona tanaman. Pemantauan dilakukan melalui web server dalam bentuk tabel dan grafik. Hasil pengujian didapatkan bahwa sistem ini dapat bekerja dengan baik. Dht22 dapat membaca suhu dan kelembaban dengan margin error dari pengukuran ini yakni suhu 0,410C dan kelembaban 2,56%. Pompa air bekerja dengan batasan yang telah ditentukan, ketika melebihi batas maka relay menyala dan pompa air bekerja. Hal ini sudah sesuai dengan yang diharapkan. Pengiriman data hasil sensor ke server dapat membaca dengan benar, hasil pengujian nilai sensor pada serial monitor dan di web server memiliki nilai yang sama, meskipun teradi delay. Web server dapat menampilkan data suhu dalam bentuk grafik dan tabel. Suhu dan kelembaban ideal berhasil berhasil dilakukan. Rata-rata suhu dan kelembaban ruangan sebelum menggunakan sistem yakni 30.20C dan 56,86%. Sedangkan rata-rata suhu dan kelembaban ruangan setelah menggunakan sistem yakni 27.850C dan 73,99%. Hal ini menunjukkan bahwa terjadi penurunan rata-rata suhu sebesar 2.350C dan kenaikan kelembaban sebesar 17.13%.AbstractAglaonema is a leaf ornamental plant that has a beauty value on the variation of leaves, both color and leaf shape motif. Aglaonema grows at 24-270C and humidity 65-75%, and it’s not exposed to direct sunlight. To get ideal conditions aglaonema placed in a greenhouse. So designed a system that can monitor the temperature, humidity and control of plant watering automatically on the greenhouse. The tools used to design this system are DHT22 sensor, arduino uno microcontroller, relay, selenoid valve, ethernet shield and water pump. The sensors are placed in 3 loacations within the greenhouse in the roof zone, the wall zone and the plant zone. Monitoring is done through a web server in the form of tables and graphs. Test results found that this system can work well. Dht22 can read the temperature and humidity with the error margin of this measurement ie temperature of 0.410C and humidity 2,56%. The water pump works with a predetermined limit, when it exceeds the limit the relay lights up and the water pump works. This is as expected. Delivery of the sensor data to the server can read correctly, the test results of sensor values on the serial monitor and on the web server have the same value, although delay occurs. The web server can display temperature data in the form of graphs and tables. Ideal temperature and humidity successfully performed. Average temperature and humidity of the room before using the system that is 30.20C and 56.86%. While the average temperature and humidity of the room after using the system that is 27.850C and 73.99%. This shows that there is a decrease in the average temperature of 2.350C and humidity increase of 17.13%.

Numerical Simulation of the Fluid-Solid Two-Phase in the Horizontal Pipe Based on DEM-CFD Coupling Method

Compared to the conventional CFD method, the CFD–DEM coupling is proposed to simulate the solid–liquid two–phase flow in the horizontal pipe in this paper. The standard k–ε model was utilized for fluid turbulent flow, the standard wall functions for near-wall zone treatment, and the Hertz–Mindlin (no slip) model for particle–particle and particle–wall contact. The movements and distribution of particles in different inlet velocities and pressure drop in pipeline are investigated in this paper. The results show that the coarse particles appear starting, discontinuous movement as bedload, continuous movement as bedload, and suspension in order with mean velocity of fluid media increase; with the increasing inlet velocity, the distribution of partilces in the pipe becomes more even, however, the concentration of the particles on the botton is larger than that on the top. Moreover, the pressure drop predicted by this method is compared with the Churchill pressure drop model and results are not identical. Therefore, the regular of pressure drop is demonstrated in this paper.