Results Of Field Measurements Research Articles

Performance evaluation of a single-side windcatcher in the transitional seasons (case study: Khousf town, Southern Khorasan Province, Iran)

PurposeLife experience in hot and arid areas of Iran has proved that in the transitional seasons (spring and autumn) in which the climate is not too hot, passive cooling systems such as windcatchers (baadgir) have functioned well. This paper intends to investigate the efficiency of a single-side windcatcher as a passive cooling strategy; the case study is the Bina House windcatcher, located in Khousf town, near Birjand city, Iran.Design/methodology/approachTo achieve the aim, air temperature, relative humidity, wind data and mean radiant temperature were measured by the related tools over five days from September 23 to October 23. Then, the thermal performance of the windcatcher was examined by analyzing the effects of all these factors on human thermal comfort. Quantitative assessment of the indoor environment was estimated using DesignBuilder and its computational fluid dynamics (CFD) tool, a thermal comfort simulation method to compare the cooling potential of the windcatcher. Windcatcher performance was then compared with two other common cooling systems in the area: single-side window, and evaporative cooler.FindingsThe results showed that both windcatcher and evaporative cooler can provide thermal comfort for Khousf residents in the transitional seasons; but the difference is that an evaporative cooler needs to consume water and electricity power, while a windcatcher is a passive cooling system that uses clean energy of wind.Originality/valueThe present study, by quantitative study of single-side windcatchers in a desert region, measured the climatic factors of a historical house and compared it with thermal comfort criteria. Therefore, the results of field measurements were analyzed, and the efficiency of the windcatcher was compared with two other cooling systems, namely single-side ventilation and evaporative cooler, in the two seasons of summer and autumn (transition seasons).

Empirical Pathloss Model Analysis of Television White Space in Lagos, Western Nigeria

To conduct feasible unlicensed communications in the television band, radio equipment must first identify transmission possibilities, or the proportion of the permitted spectrum for broadcasting services that is vacant at a given time in a particular location, which is referred to as Television White Space (TVWS). A drive test was conducted to determine the signal strength of three cell towers in three distinct areas of Lagos state (rural, suburban, and urban). The signal power parameters were measured in rural, urban, and suburban parts of Lagos in order to provide empirical values for the parameters that unlicensed radio devices can utilize to distinguish between vacant and occupied television channels in a real-world scenario. This research presents the results of field measurements in the UHF television band (470-860 MHz) conducted in Lagos. This work investigated and compared several propagation models (COST 231 model, Egli model, Okumura-Hata model, and Plain Earth model). The Standard Deviation Error (SDE), Root Mean Square Error (RMSE), and Mean Error (ME) analysis showed that the COST-231 Hata model is the optimal model for calculating path loss based on path loss exponents. This discovery led to the development of an improved model, the Oressuff TV model, which uses COST-231 Hata parameters to predict path loss in the 470–870 MHz spectrum for rural, urban, and suburban locations. From the result of Root Mean Square Error analysis, the proposed model predicted path loss in rural, urban, and suburban stations with low RMSE of 3.06dB, 3.08dB, and 1.19dB respectively. These figures indicate that the model optimization was successful, and that the Oressuff TV proposed model can estimate the path loss incurred by television signals with greater precision. Telecommunications firms may improve their service by utilizing the proposed model.

Review of Refractive Index-Matching Techniques of Polymethyl Methacrylate in Flow Field Visualization Experiments

The development of modern computational fluid dynamics (CFD) technology provides many preliminary references for experimental design. In addition, the CFD calculation results verified by experiments can display enormous microdata in areas that are difficult to measure through experiments, as an extension. This can make measurements more reasonable and effective, shorten measurement times, and save manpower and capital significantly. Therefore, it is vital to verify the accuracy of CFD calculation results, especially in cases of complex structures and multiphase flows. The results of model tests can be utilized in a prototype experiment by properly designing a test section and selecting a working fluid if the Reynolds similarity criterion is met. Optical measurement technology is a noninvasive measurement method, and the impact on the flow field can be almost negligible. It is advised to use transparent materials and prepare a refractive index-matching (RIM) fluid to obtain a good optical path. Polymethyl methacrylate (PMMA) is widely used in flow field visualization experiments because of its good light transmission and mechanical strength. This review is aimed at introducing the current status of different flow field measurement techniques; moreover, it is intended to help the readers to become more familiar with the principles of RIM, the characteristics, applications, and usage suggestions of various RIM fluid schemes of PMMA, providing references for researchers in the design, preparation, and conducting stages of flow field visualization measurement experiments. This review is divided into five sections. In the introduction section, Chapter 1, relevant research developments and related results of flow field measurements are presented, followed by the innovations and benefits of this paper. In Chapter 2, the flow field visualization measurements are presented and a derivation is shown. In Chapter 3, some RIM fluid schemes of PMMA and their applications are given, which are very valuable for peers. In Chapter 4, the measurement and analysis of some physical properties are described. In the RIM process, it is necessary to focus on the RI, density, dynamic viscosity, compatibility, stability, safety, and cost of RIM fluids. These factors greatly impact the accuracy of experimental results, experimental progress, and safety of the experimenters. Based on the analysis and our practical experience, some suggestions are given for preparing and using RIM fluids. In the conclusion section, Chapter 5, the results and practical implications of this paper are summarized.

Base Station Energy Use in Dense Urban and Suburban Areas

Growing energy consumption is a global problem. The information and communications technology (ICT) industry is in a critical role as an enabler of energy savings in other sectors. However, the power consumption of the ICT sector also needs to be addressed, to contribute to the overall reduction of power consumption and carbon emissions. A new era has begun as the fifth generation (5G) mobile data connection rollouts are advancing globally and are expected to reach a 10% share of end-user devices and connections by 2023. The available references on energy consumption in global mobile networks are rather old and highly averaged – only estimates of energy consumption relative to data volumes are available. There is an information gap regarding the energy consumption of emerging 5G and advanced 4G technologies. Therefore, it has been difficult to understand the actual electricity consumption differences between generations and spatially aggregated electricity consumption once these generations are combined to offer capacity and coverage. This article fills this gap by providing a reference on the energy consumption of base transceiver stations for reported mobile data usage for different Radio Access Technologies; 3G, 4G and 5G respectively. To the best of our knowledge, there is no reference to scientific research on the comparison of energy intensity per square kilometer for 3G, 4G and 5G mobile radio technologies, using actual operator data. The objective of this research was to improve the understanding of the actual energy consumption of different Radio Access Technologies (RAT). The results also give insight to decision makers on when to modernize the operator radio access network. The article reports on the results of field measurements on data and visitor volumes and shares of different RATs. The research contains two statistical RAT combination cases, one representing the European average and the other Finnish mobile networks. The analyses were done for dense urban (DU) and suburban (SU) areas.

Функционирование релейной защиты фидеров контактной сети в условиях изменения инфраструктуры

The problem of ensuring stability of functioning of contact network feeders is an important aspect of the railway traction power supply system operation. The ability of the protection to function correctly in emergency and normal operating modes of the AC traction network operation directly affects the efficiency and continuity of a transportation process. The paper is devoted to assessing the impact of changes in the infrastructure of railway sections on functioning of the protectors of the contact network feeders. Regular circulation of trains of increased tonnage and length on electrified sections of AC railways involves a number of problems in operation of traction network protection devices. The article summarizes long-term observations of functioning of the feeder protectors of the contact network of operating sections of the AC railway. The results of field measurements at traction substations of the Far Eastern Railway are presented. The analysis of angular characteristics of operation of remote protectors of the contact network feeders is carried out. The efficiency of functioning of protectors with angular characteristics of operation of remote protectors of various forms in driving modes of trains of increased tonnage and length is estimated. The measures aimed at increasing the stability of functioning of the contact network feeders in various modes of operation of the traction network are evaluated.

Kajian Sirkulasi Ruang Luar Terhadap Aliran Angin Pada Permukiman Padat Taman Sari Kota Bandung

Unplanned dense settlements in the development pay little attention to the technical aspects of the building and the environment, one of which is high humidity conditions and circulation pathways. Circulation in settlements can also function as wind circulation, which can affect natural ventilation, comfort, and the health of residents. This study uses a quantitative method with a descriptive approach to describe the relationship between the circulation width variable and the wind speed variable. The results of periodic field observations and measurements are then interpreted descriptively to determine the effect of circulation width on wind flow in densely populated settlements in Taman Sari, Bandung. The results showed that outdoor circulation close to open spaces had better wind speeds compared to areas far from open spaces.

Dynamic Stray Current Measuring Methods in Urban Areas

In areas where urban tracks are used as public transportation, dynamic stray currents cause high maintenance costs for the tracks and metal structures near the tracks. S tray currents caused by rail vehicles depend on many factors (traffic density, vehicle speed, acceleration and deceleration, soil and track moisture), so it is very difficult to get a clear picture of the harmfulness of the stray current based on the results of a single field measurement. However, there are several measurement methods that can be used to determine the presence of stray currents and predict appropriate track maintenance actions. Some of these methods are described in this article, namely the use of stray current mapper, measurement of rail potential and rail current, measurement at the stray current collection system, and the use of non-destructive sensors. In track construction, measuring the electrical potential between rail and ground is one of the most common methods of detecting the damaging influence of stray current.

The Matrix Model of Discrete Matching Elements for HF Computational Automatic Tuning Units

The article is devoted to a new and relevant direction in the HF communication technology - the construction of high-speed computational antenna tuning units (ATU). The implementation of automatic ATU requires the designing of power circuits models adequate, as practice shows, the construction of models to physical reality in order to ensure their controllability. Practically powerful device elements are not in fact concentrated, the distributed nature of their parameters is noticeably manifested in the HF range. Matching ATU on the base of antenna input impedance measuring involves forming of accurate control commands for the elements, especially in conditions where the settings are narrow-band. A new approach to the description of a power circuit discrete elements transforming properties using the theory of linear passive four-pole and matrices, which has the ultimate accuracy, is proposed. A method to form a matrix description of on-off discrete elements of a power circuit based on the results of characteristic field measurements of the mounted device is presented. This approach made it possible to significantly reduce the amount of tabulated data describing the functional dependences of the complex coefficients of wave transmission matrices and to “smooth out” the experimental error. Complex cases are considered, which are of the greatest interest for practice - options for a four-pole cascade and parallel connection of reactive elements in the branches of the power circuit. The current state of computer technology makes it possible to sharply increase the complexity of the mathematical models used. The matrix model takes into account a significant variety of operating factors and does not require them to be “customized” to existing analytical methods. The adequacy, in this simulation, is determined by practical needs that arise in the design of power circuits of matching antenna devices and their tuning algorithms. In fact, the model is considered adequate if the errors in the calculation of the response function according to the model do not exceed the errors in its experimental determination. The proposed matrix approach made it possible to significantly improve the accuracy of modeling, while the error does not exceed 1 %. Also, this approach allows to find several options for setting a given quality and choose the best one for any parameter, while reducing the duration of the process up to 25 times. At the additional metrological advantages appeared in such devices serial production.

The effect of the Madden–Julian Oscillation on the global electric circuit

The Madden–Julian Oscillation (MJO) is the most dominant component of the climate variability in the tropics on the timescale of tens of days. Occurring irregularly, the MJO consists of an eastward propagation of certain large-scale coupled structures in atmospheric circulation and deep convection. Here we investigate the effect of the MJO on the direct current global electric circuit (GEC), using both numerical simulations and the results of electric field measurements. We have reproduced the atmospheric dynamics for 1980–2020 with the help of the Weather Research and Forecasting model and meteorological reanalysis data; this allowed us to simulate 41 years of the GEC variation by parameterising contributions to the ionospheric potential (IP) in terms of precipitation and convection. Besides, we have analysed the results of surface potential gradient (PG) measurements at the Vostok station in Antarctica during 2006–2020. When averaged over many days, both the simulated IP and measured fair-weather PG show sinewave-like variations with the MJO phase, which manifest a statistically significant correlation with the MJO cycle. A more elaborate investigation involving an application of empirical orthogonal functions shows that the dynamics of contributions to the IP follows the patterns of variability of deep convection typical for the MJO. The variation of the IP on the MJO scale can largely be represented as a superposition of two basic oscillating patterns of convection, one of which is located over the Maritime Continent and its surrounding seas and the other is located over the Indian Ocean and part of South-East Asia. These oscillating patterns together describe the eastward progression of perturbations and can be naturally associated with the two components of the Real-time Multivariate MJO index, widely used to describe the MJO. Together with earlier results about links between the GEC and the El Niño—Southern Oscillation, the results concerning the MJO obtained in this study indicate that the GEC is an important part of the Earth system, which reflects climate variability on different timescales.

Association of indoor temperature and air quality in classrooms based on field and intervention measurements

To investigate the variation of classroom environment during typical lecture hours, repeated field measurements and intervention experiments for indoor temperature were carried out in a typical class (95 min in duration, 0.32–0.39 person/m2 of occupants density) in a spring semester of a university in Beijing. Environmental data were recorded every 5 min, including indoor temperature, relative humidity and carbon dioxide (CO2) concentration. Additionally, volatile organic compounds (VOCs) were sampled and indoor air quality (IAQ) were evaluated repeatedly. The results of field measurements showed the average air temperature in the classroom ranged from 21.2 ± 0.8 °C to 26.8 ± 0.7 °C, relative humidity ranged from 23.1 ± 1.8% to 57.5 ± 0.2%, and the average concentrations of CO2 and total volatile organic compounds (TVOC) were 1,291–1,833 ppmv and 159-1,178 ppbm respectively. The subjective evaluations collected during intervention experiments showed that perceived odor intensity by visitors upon entering the room increased significantly, meanwhile the satisfaction and acceptability of air quality reduced considerably at the indoor temperature of 27 °C than that at 24 °C. Present results suggest when the indoor temperature rises, it is necessary to increase the outdoor air supply rate to ensure air freshness in classrooms. Subsequently, the calculated CO2 emission rate by students increased by 0.54 L/h per person for every 1 °C rise in indoor temperature. Corresponding to the control target of indoor CO2 concentration of 1,000 ppmv, the outdoor air ventilation rate required to eliminate occupant-generated pollution needs to be increased by 0.25 L/s per person.

Statistical Features of Georadar Signals Obtained by Probing Horizontal Layered Media in Permafrost

Relevance. To study the structure and properties of rock masses in the permafrost zone, such a method of geophysics as ground penetrating radar is successfully used. The existing methods of GPR measurements make it possible to obtain large volumes of reliable data on the layered structure of permafrost rocks. The methodological support for processing and interpreting data is developed much worse. Thus, manual and semi-automatic methods are used to identify the in-phase axes of georadar signals confined to the boundaries of rock layers, which significantly slows down the process of cameral work. Existing methods for automating the selection of in-phase axes of georadar signals do not always successfully cope with this task, since the statistical characteristics of georadar traces obtained by probing a horizontally layered media are very variable. The purpose of the research is to establish the statistical features of georadar signals that form the in-phase axes obtained by probing horizontally layered media in permafrost. Research methods – statistical analysis of the results of field georadar measurements in the Anabar region of the Republic of Sakha (Yakutia) at the site of the Mayat diamond deposit (AO Almazy Anabara) using the GPR OKO ABDL-Triton. Conclusions. The research of the amplitude characteristics of GPR signals that form the in-phase axes showed the presence of a random component, which significantly affects the recorded GPR wave field. Using the results of field measurements of horizontally layered media as an example, a change with increasing depth of the main statistical characteristics, as well as the distribution of amplitude values (normal–uniform–normal) was established. The results obtained will be very useful both in interpreting georadar measurement data and in improving the accuracy of modeling the propagation of ultra-wideband electromagnetic waves in horizontally layered media, and can also be used to refine the previously developed model of a georadar section of a frozen rock mass.

Assessment of Greenhouse Gas Emissions into the Atmosphere from the Northern Peatlands Using the Wetland-DNDC Simulation Model: A Case Study of the Great Vasyugan Mire, Western Siberia

The peatlands of Western Siberia occupy an area of about 1 million km2 and act as important regulator of carbon exchange between the earth and the atmosphere. Extrapolation of the results of discrete field measurements of CO2 fluxes in bog ecosystems to such a territory is a difficult task, and one of the ways to overcome it is to use a simulation model such as DNDC. However, using this model with a specific territory requires ground verification to confirm its effectiveness. Here, we tested the DNDC model on the largest pristine bog ecosystem of the world, the Great Vasyugan Mire (GVM). The GVM of western Siberia is virtually undisturbed by anthropogenic activity and is the largest bog of Northern Eurasia (53,000 km2). Based on various ground-based observations, the performance of the Wetland-DNDC model was demonstrated (Thale coefficient 0.085 and R2 = 0.675 for CO2). Model input parameters specific to the GVM were constrained and model sensitivity to a wide range of input parameters was analyzed. The estimated annual terrestrial carbon fluxes in 2019 from the GVM test site are mainly controlled by plant respiration (61%) and forest floor degradation (38%). The net CO2 emission flux was 8600 kg C ha−1 year−1, which is in line with estimates from other independent studies.

Sensitivity Analysis of Influencing Factors of Underground Civil Air Defense Construction Vibration under Vehicle Load

Grey correlation theory is an uncertainty analysis method, which can find the relevance of various factors studied through certain data processing in incomplete information and find the main influencing factors. In order to study the influence of vehicle load on the vibration of underground civil air defense construction, taking the civil air defense construction at the intersection of Zhongzhou Middle Road and Shachang South Road in Luoyang as the study subject, based on the field measured data, and using ANSYS to expand the working conditions, this paper studies the influence of such factors as elastic modulus of concrete, thickness of overburden layer, density of soil layer, elastic modulus of soil layer, vehicle speed, and vehicle mass on the vibration of the civil air defense construction through the grey correlation sensitivity analysis method. The field measurement and numerical simulation results show that the displacement, velocity, and acceleration values decrease gradually from the mid−span position of the roof to the wall. Displacement, velocity, and acceleration are important indexes for evaluating vibration. The grey correlation degree of the influencing factors of displacement and velocity from large to small is density of soil layer, vehicle mass, vehicle speed, elastic modulus of concrete, elastic modulus of soil layer, and thickness of overburden layer. The grey correlation degree of the influencing factors of acceleration from large to small is vehicle mass, layer of density of soil layer, vehicle speed, elastic modulus of concrete, elastic modulus of soil layer, and thickness of overburden layer. The grey correlation degree of soil layer density, vehicle mass and vehicle speed to displacement, velocity, and acceleration is 0.7951–0.9993, which indicates that their influence is significant. This study can provide reference for the design and construction of similar civil air defense constructions.

Твердые частицы как индикатор размещения постов наблюдения за загрязнением атмосферы в Мурманске

The article presents the results of field measurements and analysis of atmospheric air samples at 25 characteristic points on the territory of Murmansk in 2017—2018. For all particles taken from atmospheric air the researchers determine the granulometric, morphological and chemical composition using a high-resolution scanning electron microscope S-3400N Hitachi. They consider meteorological conditions as of the dates of sampling from the point of view of their effect on the dispersion of pollutants. The results made it possible to preliminary determine the regions on the territory of Murmansk that are most and least dependent on meteorological conditions, as well as to formulate recommendations for improving the atmospheric air monitoring network in Murmansk.

Multiple Marangoni flows in a binary mixture sessile droplet

A multicomponent droplet evaporation problem has widely been investigated due to diverse industrial applications, including ink-jet printing, surface coating and patterning, medical diagnosis, spraying cooling, and fuel combustion. During evaporation, the Marangoni flow caused by selective evaporation should be observed, and it plays an important role in determining the drying process and the final dried deposit pattern. However, most of the works focused on measuring the internal flow field although the Marangoni flow mainly occurred near the liquid–gas interface. In this study, using particle image velocimetry, we tried to measure the interfacial Marangoni flows where the measurement focal plane was set in the vicinity of the apex of the binary mixture droplet. We observed distinctive multiple Marangoni flows in time, such as (i) directional circulating flow, (ii) complicated mixing flow, and (iii) spontaneous bursting flow. Finally, we found that the Reynolds number is different for each case. Based on the flow field measurement result and dimensionless number analysis, we considered a stress balance model that qualitatively described the local surface tension gradient and Marangoni stress.

Numerical Analysis of Factors Influencing the Ground Surface Settlement above a Cavity

In this study, ground stability was evaluated through vertical displacement distribution and surface settlement results. In particular, a finite element analysis was conducted considering various factors (namely, cavity type and area, traffic load, pavement thickness, and elastic modulus) that affect a road above a cavity. The aim of this study was to evaluate the effect of pavement layer and traffic load condition on surface settlement according to the cavity shape. Field measurement results were analyzed and compared with the results of previous studies to verify the reliability of the numerical analysis method applied herein. After performing the numerical analysis using the verified method, ground stability was evaluated by analyzing the underground mechanical behavior of a road above a cavity. To this end, the correlations among the vertical displacement distribution, surface settlement, and influencing factors obtained from the analysis results were analyzed. In the numerical analysis, the ground was simulated with a hardening soil model based on the elastoplastic theory. This mechanical soil model can accurately reproduce the behavior of actual ground and can closely represent the mechanical behavior of the soil surrounding a cavity according to the cavity generation. In addition, the elapsed time was not considered when applying a load on the pavement layer, and a uniformly distributed load was applied. Consequently, it was found that, with increasing cavity area and traffic load and decreasing pavement thickness and elastic modulus, the vertical displacement and maximum surface settlement above the cavity increased, and the reduction in ground stability was greater. Furthermore, the reduction in ground stability was greater when the cavity was rectangular than when it was circular.

Assessment and prioritization of soil erosion triggering factors using analytical hierarchy process and Taguchi method

The main aims of this study are assessing some factors which affect the soil erosion process and evaluating the results of an analytical hierarchy process (AHP) method using the Taguchi method. Firstly, the weights for those factors and levels affecting soil erosion were determined by the AHP method. The determination of weights was based on the opinions of academic researchers, experts, middle managers, and members of the Soil and Water Research Centers in Iran. Secondly, an L32 Taguchi orthogonal array was selected based on the number of factors and levels for the current problem. Accordingly, 32 rainfall events were simulated and sediment yield amounts were measured. Analyzing the results of the Taguchi method, the weights of factors and levels were determined. The results showed that the weights obtained from the AHP method were not in accordance with the results of field measurements and the Taguchi analysis. The AHP method indicated that the main factors have the following order of importance: geological formation, rainfall intensity, silt content of soil as an indicator for the soil texture, vegetation cover, slope steepness, and slope aspect in the study area. However, the Taguchi method found the following order for the main factors: rainfall intensity, geological formation, silt content of soil as an indicator for the soil texture, slope steepness, vegetation cover, and slope aspect. As the Taguchi method works based on the quantitative measurements, the Taguchi results are more reliable rather than subjective methods such as AHP. It was also concluded that the AHP method should be used cautiously in assessing natural phenomena. Therefore, in the cases that in situ measurements are possible, it is better to use quantitative mathematical and statistical methods than to rely to qualitative knowledge based approaches.

Calibration of coherent optical fiber bundle with LCD screen for deformation measurements

Owning to its flexibility, high temperature resistance, and freedom from electromagnetic interference, coherent optical fiber bundle (COFB) is widely used in special imaging applications. However, limited by the manufacturing process, the fiber arrangement of COFB is prone to misalignment, resulting in imaging distortions that are not easily corrected. This limits the application of COFB in the field of optical measurement, making it difficult to meet the requirements of high-precision deformation measurement. To effectively calibrate the misalignment distortion and recover the original image information, this study proposes an easy-to-implement and highly accurate misalignment distortion calibration method. The LCD screen was used as the calibration reference to display a pre-designed regular arrangement pattern. The mapping relationship between the fiber output and the screen display information was confirmed using a correlation algorithm. The proposed method requires only 36 images to achieve misalignment calibration for 450 × 450 fibers. The image reconstruction results show that the proposed method can not only achieve global misalignment calibration, but also successfully eliminate honeycomb artifacts, thus enhancing the accuracy and practicality of COFB for deformation measurement. In addition, a COFB-based digital image correlation (DIC) system was established and a set of typical DIC experiments were implemented. The experimental results show that the proposed calibration method can significantly improve the deformation measurement accuracy of the COFB-based DIC system, and the accuracy of the two-dimensional (2D) displacement field measurement result is improved from 0.50 pixels to 0.03 pixels.

Research on the Development Law of Water-Conducting Fracture Zone in the Combined Mining of Jurassic and Carboniferous Coal Seams

The accurate prediction of the height of the water-conducting fracture zone is essential for the prevention of roof damage by water disasters in coal mines. The development law of water-conducting fracture zone in combined mining of Jurassic and Carboniferous coal seams is different from that of previous research results. This study constructed an engineering geomechanics model to carry out material simulation and numerical simulation. The changes of stress, displacement, and fracture propagation were analyzed and compared with the results of formula calculation and field measurement, revealing the combined action of Jurassic and Carboniferous coal seams on the development law of water-conducting fracture zone. The results show that: (1) stress concentration is formed in the middle of the goaf in Jurassic coal seam, resulting in the high height of water-conducting fracture zone and the fracture “closed”; (2) the mining of Carboniferous coal seams caused the second subsidence of Jurassic goaf, and closed fracture “activated”; (3) the height of the water-conducting fracture zone obtained by the empirical formula is small, which is quite different from the actual situation. These research results are of significance for determining the height of the water-conducting fracture zone in Jurassic and Carboniferous coal seams during combined mining and the prevention of coal roof water hazards.

Empirical modeling of the distribution of chlorophyll-a in riam kanan reservoir

Monitoring inland water quality through remote sensing is an alternative method. Broad remote sensing image coverage has the potential to increase the scope of monitoring. Remote sensing imagery is very suitable for monitoring in the Riam Kanan Reservoir which has a normal water level of 3200 Ha. Community activities for fisheries and tourism have the potential to increase nutrients and water fertility. The impact is in the form of an explosion of algal micro population which has a negative effect on the aquatic ecosystem and the surrounding population. Landsat 8 OLI was used in this study to determine the level of chlorophyll-a content in reservoir waters. Empirical modeling is a method for modeling the distribution of chlorophyll-a content utilizing the results of field measurements. Through this method also can be known which spectral band has an influence in monitoring the chlorophyll-a so that it can be seen the level of water fertility in the Riam Kanan reservoir.