Effects of fracture aperture and roughness on hydraulic and mechanical properties of rocks : implication of seismic characterization of fractured reservoirs

Roughness and aperture are two important characteristic parameters controlling fluid flow in natural joints and fractures. It has been demonstrated by many authors that knowledge of roughness does not directly lead to that of aperture, and aperture should be handled as a separate geometrical descriptor. To determine the normal deformability and flow response of a fracture, the aperture distribution and the mechanical properties of the rock matrix are required. When shearing of joints and fractures is considered, roughness comes into play and affects the evolution of the aperture distribution. The aperture distribution can be evaluated by knowing the correlation between the asperity profiles of the rock walls of a rock fracture. Thus, the distributions of contact area and void space determine the fracture dilation and hydraulic properties during shearing. In the seismic characterization of fractured reservoirs, various equivalent medium theories describing the effective elastic properties of fractured media have been proposed. One relatively simple theory is based on the assumption of the linear slip interface or displacement discontinuity model of fractures. Two parameters are usually used in the linear slip interface model: the normal and shear fracture compliances defined as the ratio of normal (shear) displacement discontinuity and normal (shear) stress. Fracture compliances are by definition functions of mechanical aperture and are also influenced by the roughness (surface asperity distribution) of fracture surfaces. In this study, I investigate the effects of fracture roughness and apertures on the hydraulic and mechanical properties of fractured rock. Specifically, I focus on two kinds of fracture models which are commonly used in describing the effective hydraulic and mechanical (elastic) response of natural fractures. The first is the rough-walled fracture model and the second is an interface with distributions of contacts and voids (called the asperity fracture model)

Fertilizer Use in China: The Role of Agricultural Support Policies

Using a decomposition method, this paper proposes an analytical framework to investigate the mechanisms by which agricultural support policies affect farmers’ use of fertilizers in agriculture in China. The mechanisms are decomposed into “three effects” (structural, scale, and technological effects). It is found that China’s agricultural support polices have significantly contributed to the increased use of agricultural fertilizers through encouraging farmers to bring more land under cultivation (the scale effect). Meanwhile, some policies have also helped reduce fertilizer consumption when farmers were motivated to increase the area of grains crops (the structural effect). The role of technological progress in affecting fertilizer consumption (the technological effect) appears to be minimal and uncertain. Compared to direct subsidies, indirect subsidies play a much greater role in affecting farmers’ production decision making and are more environmentally consequential. This paper argues that some of China’s agricultural support policies are not well aligned with one key objective of the country’s rural policies—improving environmental sustainability. It is recommended that the government takes measures to reform agricultural support policies and to reconcile agricultural and rural policies in order to achieve sustainable rural development

The Effect of Abstract vs. Realistic 3D Visualization on Landmark and Route Knowledge Acquisition

Even though humans perform it daily, navigation is a cognitively challenging process. Landmarks have been shown to facilitate navigation by scaffolding humans’ mental representation of space. However, how landmarks can be effectively communicated to pedestrians to support spatial learning of the traversed environment remains an open question. Therefore, we assessed how the visualization of landmarks on a mobile map (i.e., abstract 3D vs. realistic 3D symbols) influences participants’ spatial learning, visual attention allocation, and cognitive load during an outdoor map-assisted navigation task. We report initial results on how exposing pedestrians to different landmark visualization styles on mobile maps while navigating along a given route in an urban environment can have differing effects on how they remember landmarks and routes. Specifically, we find that navigators better remember landmarks visualized as 3D realistic-looking symbols compared to 3D abstract landmark symbols on the mobile map. The pattern of results shows that displaying realistic 3D landmark symbols at intersections potentially helps participants to remember route directions better than with landmarks depicted as abstract 3D symbols. The presented methodological approach contributes ecologically valid insights to further understand how the design of landmarks on mobile maps could support wayfinders' spatial learning during map-assisted navigation

Using spontaneous eye blink-related brain activity to investigate cognitive load during mobile map-assisted navigation

The continuous assessment of pedestrians’ cognitive load during a naturalistic mobile map-assisted navigation task is challenging because of limited experimental control over stimulus presentation, human-map-interactions, and other participant responses. To overcome this challenge, the present study takes advantage of navigators’ spontaneous eye blinks during navigation to serve as event markers in continuously recorded electroencephalography (EEG) data to assess cognitive load in a mobile map-assisted navigation task. We examined if and how displaying different numbers of landmarks (3 vs. 5 vs. 7) on mobile maps along a given route would influence navigators’ cognitive load during navigation in virtual urban environments. Cognitive load was assessed by the peak amplitudes of the blink-related fronto-central N2 and parieto-occipital P3. Our results show increased parieto-occipital P3 amplitude indicating higher cognitive load in the 7-landmark condition, compared to showing 3 or 5 landmarks. Our prior research already demonstrated that participants acquire more spatial knowledge in the 5- and 7-landmark conditions compared to the 3-landmark condition. Together with the current study, we find that showing 5 landmarks, compared to 3 or 7 landmarks, improved spatial learning without overtaxing cognitive load during navigation in different urban environments. Our findings also indicate a possible cognitive load spillover effect during map-assisted wayfinding whereby cognitive load during map viewing might have affected cognitive load during goal-directed locomotion in the environment or vice versa. Our research demonstrates that users’ cognitive load and spatial learning should be considered together when designing the display of future navigation aids and that navigators’ eye blinks can serve as useful event makers to parse continuous human brain dynamics reflecting cognitive load in naturalistic settings

The effect of landmark visualization in mobile maps on brain activity during navigation: A virtual reality study

The frequent use of GPS-based navigation assistance is found to negatively affect spatial learning. Displaying landmarks effectively while providing wayfinding instructions on such services could facilitate spatial learning because landmarks help navigators to structure and learn an environment by serving as cognitive anchors. However, simply adding landmarks on mobile maps may tax additional cognitive resources and thus adversely affect cognitive load in mobile map users during navigation. To address this potential issue, we set up the present study experimentally to investigate how the number of landmarks (i.e., 3 vs. 5 vs. 7 landmarks), displayed on a mobile map one at a time at intersections during turn-by-turn instructions, affects spatial learning, cognitive load, and visuospatial encoding during map consultation in a virtual urban environment. Spatial learning of the environment was measured using a landmark recognition test, a route direction test, and Judgements of Relative Directions (JRDs). Cognitive load and visuospatial encoding were assessed using electroencephalography (EEG) by analyzing power modulations in distinct frequency bands as well as peak amplitudes of event-related brain potentials (ERPs). Behavioral results demonstrate that landmark and route learning improve when the number of landmarks shown on a mobile map increases from three to five, but that there is no further benefit in spatial learning when depicting seven landmarks. EEG analyses show that relative theta power at fronto-central leads and P3 amplitudes at parieto-occipital leads increase in the seven-landmark condition compared to the three- and five-landmark conditions, likely indicating an increase in cognitive load in the seven-landmark condition. Visuospatial encoding indicated by greater theta ERS and alpha ERD at occipital leads with a greater number of landmarks on mobile maps. We conclude that the number of landmarks visualized when following a route can support spatial learning during map-assisted navigation but with a potential boundary—visualizing landmarks on maps benefits users’ spatial learning only when the number of visualized landmarks shown does not exceed users’ cognitive capacity. These results shed more light on neuronal correlates underlying cognitive load and visuospatial encoding during spatial learning in map-assisted navigation. Our findings also contribute to the design of neuro-adaptive landmark visualization for mobile navigation aids that aim to adapt to users’ cognitive load to optimize their spatial learning in real time

ANALISIS PENGENDALIAN PERSEDIAAN AYAM BROILER HIDUP DENGAN PENDEKATAN METODE ECONOMIC ORDER QUANTITY (EOQ)

ABSTRAK Perkembangan usaha di Indonesia adalah salah satu yang menjadi tulang punggung bagi perekonomian nasional, salah satu contoh usaha yang kini mengalami perkembanganyang sangat pesat dan memiliki permintaan pasar yang cukup luas yaitu usaha distributorayam hidup. PT.Angga Putra Mandiri adalah perusahaan yang bergerak dalam bidangdistributor ayam broiler hidup. Permasalahan yang sering terjadi yaitu sering mengalamikeadaan kekurangan bahan baku ayam broiler hidup sehingga usaha ini sering mengalamikeadaan kekurangan bahan baku ayam hidup pada saat operasionalnya. Berdasarkan hasildata observasi, yang dilakukan di PT.Angga Putra Mandiri, yaitu terlalu besar biayapemesanan dan penyimpanan sehingga bisa dapat merugikan perusahaan selamaoperasional yang dijalankan. Dari permasalahan tersebut maka dapat dilakukannyapemecahan masalah dengan membandingkan penghitungan dengan menggunakan metodeEconomic Order Quantity, sehingga dapat hasil yang lebih hemat agar operasional lebihefisien. Hasil analisis data yang telah didapatkan bahwa kuantitas pembelian bahan bakuayam hidup menggunakan metode EOQ adalah sebesar 2,014,6 Kg dengan frekuensipembelian sebanyak 241 kali, safety stock sebesar 67,5 Kg dan ROP dilakukan pada saatbahan baku ayam broiler hidup dikandang sebesar 1.450 Kg sedangkan total biayapersediaan sebesar 10.217.554,3 pada tahun 2018.Kata Kunci: Pengendalian Persediaan, Economic Order Quantity (EOQ), Ayam Broile

Boundary integral modelling of elastic wave propagation in multi-layered 2D media with irregular interfaces

We present a semi-analytic method based on the propagation matrix formulation of indirect boundary element method to compute response of elastic (and acoustic) waves in multi-layered media with irregular interfaces. The method works recursively starting from the top-most free surface at which a stress-free boundary condition is applied, and the displacement-stress boundary conditions are then subsequently applied at each interface. The basic idea behind this method is the matrix formulation of the propagation matrix (PM) or more recently the reflectivity method as wide used in the geophysics community for the computation of synthetic seismograms in stratified media. The reflected and transmitted wave-fields between arbitrary shapes of layers can be computed using the indirect boundary element method (BEM, sometimes called IBEM). Like any standard BEM, the primary task of the BEM-based propagation matrix method (thereafter called PM-BEM) is the evaluation of element boundary integral of the Green's function, for which there are standard method that can be adapted. In addition, effective absorbing boundary conditions as used in the finite difference numerical method is adapted in our implementation to suppress the spurious arrivals from the artificial boundaries due to limited model space. To our knowledge, such implementation has not appeared in the literature. We present several examples in this paper to demonstrate the effectiveness of this proposed PM-BEM for modelling elastic waves in media with complex structure