Understanding Surface Water--Groundwater Connectivity and Discharge in Arctic Deltas

Increased warming is driving unprecedented hydrologic changes within arctic deltas with implications for water storage, solute processing, and terrestrial and marine ecology. Thermokarst lakes within Arctic deltas store flood waters and filter solutes and sediments, thus moderating the impact of flood water discharge to arctic seas. However, this moderating influence is diminishing as lakes shrink on annual and seasonal time scales, especially close to active channels where lakes are shrinking most rapidly. This study investigates surface water-groundwater connectivity in arctic delta plains with coupled flow and heat transport models to provide a mechanistic understanding of how lake-channel proximity will impact aquifer connectivity and associated groundwater discharge to downgradient channels. Results show near-channel lakes have increased lake-to-channel advective heat transport and perennial connectivity and discharge to downgradient channel. However, connectivity and discharge from far-channel lakes is seasonal, where near-zero discharge occurs when lake and channel taliks are isolated. Near-channel lakes are perennially draining through taliks contributing to observed increases in Arctic channel baseflow. Lake drainage highlights the importance that lakes – especially near-channel lakes most vulnerable to loss – will have changing roles in moderating flood waters and nutrient processing before discharging to the arctic seas

Effects of advera® warm mix additive on the rheological properties of unaged and short term aged asphalt binders

The performance of asphalt pavement is mainly governed by the properties of the binder. Many asphalt pavement distress are pronounced to be related to the rheological properties of asphalt binder. The oxidation changes the structure and composition of asphalt binder resulting stiffer and brittle of asphalt. This paper described SuperpaveTM binder that was used to characterize the rheological properties of PG64 asphalt binders blended with various Advera® contents subjected to unaged and short term aged. Rotational viscometer (RV) and Dynamic Shear Rheometer (DSR) were conducted to measure binder properties at higher and intermediate temperature respectively. The results indicated that, the addition of Advera® in the asphalt binder exhibited change in binder rheology which influenced rutting parameteryKeywords: Advera®; Aging; Viscosity; Rotational viscometer; Dynamic shear rheometer

Facile synthesis of mesoporous N doped zirconium titanium mixed oxide nanomaterial with enhanced photocatalytic activity under visible light

The present paper deals with a hydrazine mediated synthesis of high surface area and thermally stable N-doped zirconium titanium mixed oxide with enhanced photocatalytic activity towards reduction of selenium (VI) to metallic Se0 under visible light. Materials were synthesized at pH ¼ 2 by varying the hydrazine concentration and characterized by XRD, TEM, BET method, XPS, Raman spectroscopy and UV-vis solid state spectra. Presence of low amount of zirconium oxide (10 wt%) helps in phase stabilization and maintains the porous structure even at higher calcinations temperature in comparison to that of pure titania. XPS spectrum justifies the presence of nitrogen and Ti3+ in the material due to the decomposition reaction of hydrazine. Hydrazine controls the nitrogen content, surface area and the formation of oxygen vacancy in the material. Investigation of metal oxide to hydrazine ratio on the overall surface properties and photocatalytic activity indicates that the 1 : 6 ratio is the optimum composition for the best result. Surface area and pore volume increases to 298 m2/g and 0.323 cm3/g. The obtained material (TiZr-6N-400) is found to reduce selenium (VI) to selenium (0) under visible light within only 45 min of reaction. Increased photocatalytic activity under visible light is mostly due to the synergistic effect of substantial nitrogen doping, high surface area and presence of oxygen vacancy

Pengaruh Strategi Project Based Learning (Pjbl) terhadap Kemampuan Berpikir Kritis Siswa Kelas XI IPA pada Materi Koloid

The 21st century education aims to develop the ability of intelligence of students in order to resolve the problems faced in real life. Project-Based Learning is one instructional strategies to develop the skills required in the 21st century. Through a given project, students are not only required to achieve the learning objectives that have been set, but students will be trained to face the world of work that requires their ability to access, mesintesis, communicating information, and work together to solve complex problems so as to improve the ability of students critical thinking. This research is a quasi-experimental research (quasy experiment) with posttest only control group design. This research aims to determine the influence of Project Based Learning Strategy (PjBL) to the critical thinking skills of students of class XI IPA at SMAN 1 Malua on colloidal material. The research population includes students of class XI IPA at SMAN 1 Malua, with random cluster sampling technique sampling. Data were analyzed using independent sample t-test in SPSS 20 for windows at the 0.05 level of significance. The result showed that the significance level of critical thinking skills of 0.001 which indicates that there are differences between students' critical thinking skills that learned using a strategy of Project Based Learning (PjBL) with students that learned using conventional methods.Pendidikan abad 21 bertujuan untuk membangun kemampuan intelegensi siswa dalam pembelajaran agar mampu menyelesaikan permasalahan yang dihadapi. salah satu strategi pembelaj aran di abad 21 yang mengembangkan keterampilan siswa ialah Project Based Learning. Melalui proyek yang diberikan, siswa tidak hanya dituntut untuk mencapai tujuan pembelajaran yang telah ditetapkan, tetapi siswa akan lebih terlatih menghadapi dunia kerja yang membutuhkan kemampuan mereka dalam mengakses, mesintesis, mengomunikasikan infomasi, dan bekerja sama memecahkan masalah yang kompleks sehingga dapat meningkatkan kemampuan berpikir kritis siswa. Penelitian ini merupakan penelitian eksperimen semu (quasy experiment) dengan rancangan penelitian posttest only control group design. Penelitian ini bertujuan untuk mengetahui pengaruh strategi Project Based Learning (PjBL) terhadap kemampuan berpikir kritis siswa kelas XI IPA di SMAN 1 Malua pada materi koloid. Populasi penelitian meliputi siswa kelas XI IPA SMA Negeri 1 Malua, dengan teknik pengambilan sampel cluster random sampling. Data dianalisis menggunakan independent sample t-test pada program SPSS 20 for windows pada taraf signifikasi 0,05. Hasil analisis data menunjukkan bahwa taraf signifikasi kemampuan berpikir kritis sebesar 0,001 yang menunjukkan bahwa terdapat perbedaan kemampuan berpikir kritis antara siswa yang dibelajarkan menggunakan strategi Project Based Learning (PjBL) dengan siswa yang dibelajarkan menggunakan metode konvensional

Physical Characterization of Modified Asphalt Binder with Differing Fly Ash Geopolymer Contents

Nowadays, the use of waste material product has gained popularity in the production of asphalt mixes and becomes a cost-effective method of pavement construction that can decrease the consumption of natural resources and to reduce environmental pollution. This research aimed to investigate the possibility of using waste and by-product material namely fly ash geopolymer additive to influence the physical properties of asphalt binder. An experimental matrix of laboratory testing was conducted to study the properties of the 60/70 and 80/100 asphalt binder with modified binder containing 3%, 5%, 7%, 9% and 11% of fly ash geopolymer additive. The physical properties of the binders were determined using the penetration, softening, penetration index, ductility, and rotational viscosity respectively. The results indicated that, the fly ash geopolymer modified binder had improved the physical properties over base binder. The thermal susceptibility also improved by referring to the Penetration Index value. Overall research conclusions are that geopolymer application resulted in a potential enhancement of some of the properties of the asphalt binder and increase the performance of asphalt binder in the pavement application

Physical Characterization of Modified Asphalt Binder with Differing Fly Ash Geopolymer Contents

Nowadays, the use of waste material product has gained popularity in the production of asphalt mixes and becomes a cost-effective method of pavement construction that can decrease the consumption of natural resources and to reduce environmental pollution. This research aimed to investigate the possibility of using waste and by-product material namely fly ash geopolymer additive to influence the physical properties of asphalt binder. An experimental matrix of laboratory testing was conducted to study the properties of the 60/70 and 80/100 asphalt binder with modified binder containing 3%, 5%, 7%, 9% and 11% of fly ash geopolymer additive. The physical properties of the binders were determined using the penetration, softening, penetration index, ductility, and rotational viscosity respectively. The results indicated that, the fly ash geopolymer modified binder had improved the physical properties over base binder. The thermal susceptibility also improved by referring to the Penetration Index value. Overall research conclusions are that geopolymer application resulted in a potential enhancement of some of the properties of the asphalt binder and increase the performance of asphalt binder in the pavement application

MODEL DISTRIBUSI BAHAN AJAR UNIVERSITAS TERBUKA DAN IMPLEMENTASINYA

Universitas Terbuka (UT) was implementing the centralized distribution of learning material, it is not considered efficient. Therefore, the decentralized distribution system which requires warehouses at certain regional offices will be proposed. The aims of this research are (1) investigating the decentralized learning material distribution model, (2) choosing the optimal location of warehouses to minimize the cost of learning material distribution, (3) choosing the regional offices which will be served optimally by each warehouse, (4) comparing efficiency of the centralized and decentralized learning material distribution system. The distribution problem is modeled as a linear mixed integer programming problem. The model will be solved using Branch and Bound method. This study considers centralized learning material distribution system and two alternative of decentralized learning material distribution systems, which are alternative 1 and alternative 2. It is found that in 2008 the cost of the alternative 2 is lower than the centralized learning distribution system. Besides, if the demand of learning material is increasing, the alternative 2 is still less costly than the other systems

Using ensemble decision tree model to predict student dropout in computing science

Science, Technology, Engineering and Mathematics (STEM) professionals play a key role in the development of an economy. STEM workers are critical thinkers as they contribute immensely by driving innovations. There is a high demand for professionals in the STEM fields but there is also a shortage of human resource in these areas. One way to reduce this problem is by identifying students who are at-risk of dropping out and then intervening with focused strategies that will ensure that these students remain in same the programme till graduation. Therefore, this research aims to use a data mining classification technique to identify students who are at-risk of dropping out from their Computing Science (CS) degree programmes. The Random Forest (RF) decision tree algorithm is used to learn patterns from historical data about first-year undergraduate CS students who are enrolled in a tertiary institute in the South Pacific. A number of factors are used which comprise of students demographic information, previous education background, financial information as well as data about students' academic interaction. Feature selection is performed to determine which factors have greater influence in students' decision in dropping out. Cross-validation techniques are used to ensure that the models are not over-fitted. Two models were built using a 5fold and 10-fold cross-validation and the results were compared using several measures of model performance. The results show that the factors corresponding to students' academic performance in a first-year programming course had the greatest impact student attrition in CS