Experimental and Atomistic Theoretical Study of Degree of Polarization from Multi-layer InAs/GaAs Quantum Dots

Recent experimental measurements, without any theoretical guidance, showed that isotropic polarization response can be achieved by increasing the number of QD layers in a QD stack. Here we analyse the polarization response of multi-layer quantum dot stacks containing up to nine quantum dot layers by linearly polarized PL measurements and by carrying out a systematic set of multi-million atom simulations. The atomistic modeling and simulations allow us to include correct symmetry properties in the calculations of the optical spectra: a factor critical to explain the experimental evidence. The values of the degree of polarization (DOP) calculated from our model follows the trends of the experimental data. We also present detailed physical insight by examining strain profiles, band edges diagrams and wave function plots. Multi-directional PL measurements and calculations of the DOP reveal a unique property of InAs quantum dot stacks that the TE response is anisotropic in the plane of the stacks. Therefore a single value of the DOP is not sufficient to fully characterize the polarization response. We explain this anisotropy of the TE-modes by orientation of hole wave functions along the [-110] direction. Our results provide a new insight that isotropic polarization response measured in the experimental PL spectra is due to two factors: (i) TM[001]-mode contributions increase due to enhanced intermixing of HH and LH bands, and (ii) TE[110]-mode contributions reduce significantly due to hole wave function alignment along the [-110] direction. We also present optical spectra for various geometry configurations of quantum dot stacks to provide a guide to experimentalists for the design of multi-layer QD stacks for optical devices. Our results predict that the QD stacks with identical layers will exhibit lower values of the DOP than the stacks with non-identical layers.Comment: 10 pages, 7 figures, and 1 tabl

INOKULASI RHIZOBIUM INDIGENOUS DAN TAKARAN PUPUK UREA TERHADAP NODULASI DAN PERTUMBUHAN KACANG NAGARA PADA MEDIA TANAH GAMBUT

Purpose of research is to get the right levels dosage of between inoculation Rhizobium indigenous with urea fertilizer as the best combination of nodulation and growth of Nagara bean in peat medium. Design experiment used was a completely randomized design (CRD) factorial two factors. The first factor was levels dosage treatment of Inocuation Rhizobium indigenous: r0 = 0 g (without inoculation); r1 = 100 g and r2 = 200 g  kg-1 of seeds. The second factor is levels dosage of urea fertilizer: u0 = 0 kg ha-1 (without urea fertilizer); u1 = 25 kg ha-1 (25%); u2 = 50 kg ha-1 (50%); u3 = 75 kg ha-1 (75%) and u4 = 100 kg ha-1 (100%). The combination of both treatments was 12, with 3 times replication. The result showed that the interaction between inoculation Rhizobium indigenous and dosage of urea fertilizer, significant and highly significant effect on nodulation and growth of Nagara bean in peat media. Inoculation Rhizobium indigenous 200 g kg-1  of seeds with urea fertilizer 50 kg ha-1  (50%)  was the best treatment combination for nodulation and growth of Nagara bean in peat medi

Location Selection Study For Building Fish Landing Place In Districts Bukit Batubengkalisdistrict Riauprovince

The survey was conducted in July 2015, in the village Bukitbatu, Api-api andTenggayun, Bukitbatu district in Riau Province.The purpose of this study was to find thebest location suitable for fish landing building. The method used is the method review /revise the field. Can be seen from the survey data in the technical aspects, fisheries, socioeconomicand infrastructural purpose of the examination of the three villages.The location in the village Tenggayun have advantages, including the opportunity forfishing based on factors such as the number of fishing gear, fishing, the fishing fleet and thenumber of population, which is more than Bukitbatu villages and Api-api. Waters in thevillage Tenggayun fishery potential confounding factors and population factors get thehighest score compared to two other villages, with 55 points and 30 points. The final score ofthe third evaluation village consists of 187 points for Bukitbatu village, 173 points for thevillage burning and 195 points for Tenggayun village. The results of the research using thescoring method showed that the location in the village Tenggayun is the best place to build afish landing site

Application of Natural Convection for Photovoltaic Cooling and Photocatalytic Disinfection

Two investigations for improving renewable technologies are engaged. First is the examination of the enhancement of heat transfer at the rear of a hot photovoltaic panel by natural convection using various configurations and the other is analyzing a new photocatalytic collector for water heating and cleaning. A 20 Watt polycrystalline panel is exposed to indoor simulated solar light, under constant ambient temperature and stagnant wind conditions. Three configurations are considered: a partial heat sink, a water cavity and a water channel. The experimentally obtained convective heat transfer coefficients are 4.4 W•m-2•K-1 at the rear of the bare panel, 1.1 W•m-2•K-1 with the heat sink, 26.6 W•m-2•K-1 with the water cavity and 177 W•m-2•K-1 with the water channel. The channel is attached to a cold reservoir and thermosyphoning is forcing flow through it. This is an efficient method for cooling. In the second part of this study, an integrated solar photocatalytic collector is fabricated and tested. Methylene blue dye and photo-activated catalyst were mixed with the testing fluid. The results show that the system was able to disinfect 1.2 ppm of the dye in water by 80% in the presence of 127 mg•L-1 of AEROXIDE® TiO2 P90 with the thermal efficiency of ηth = 0.67 under the laboratory conditions. It was analyzed under stagnant wind conditions and the heat losses were assessed

Location Selection Study For Building Fish Landing Place In Districts Bukit Batubengkalisdistrict Riauprovince

The survey was conducted in July 2015, in the village Bukitbatu, Api-api andTenggayun, Bukitbatu district in Riau Province.The purpose of this study was to find thebest location suitable for fish landing building. The method used is the method review /revise the field. Can be seen from the survey data in the technical aspects, fisheries, socioeconomicand infrastructural purpose of the examination of the three villages.The location in the village Tenggayun have advantages, including the opportunity forfishing based on factors such as the number of fishing gear, fishing, the fishing fleet and thenumber of population, which is more than Bukitbatu villages and Api-api. Waters in thevillage Tenggayun fishery potential confounding factors and population factors get thehighest score compared to two other villages, with 55 points and 30 points. The final score ofthe third evaluation village consists of 187 points for Bukitbatu village, 173 points for thevillage burning and 195 points for Tenggayun village. The results of the research using thescoring method showed that the location in the village Tenggayun is the best place to build afish landing site

Towards visualisation of central-cell-effects in scanning-tunnelling-microscope images of subsurface dopant qubits in silicon

Atomic-scale understanding of phosphorous donor wave functions underpins the design and optimisation of silicon based quantum devices. The accuracy of large-scale theoretical methods to compute donor wave functions is dependent on descriptions of central-cell-corrections, which are empirically fitted to match experimental binding energies, or other quantities associated with the global properties of the wave function. Direct approaches to understanding such effects in donor wave functions are of great interest. Here, we apply a comprehensive atomistic theoretical framework to compute scanning tunnelling microscopy (STM) images of subsurface donor wave functions with two central-cell-correction formalisms previously employed in the literature. The comparison between central-cell models based on real-space image features and the Fourier transform profiles indicate that the central-cell effects are visible in the simulated STM images up to ten monolayers below the silicon surface. Our study motivates a future experimental investigation of the central-cell effects via STM imaging technique with potential of fine tuning theoretical models, which could play a vital role in the design of donor-based quantum systems in scalable quantum computer architectures.Comment: Nanoscale 201

Manajemen Kepala Sekolah dalam Upaya Peningkatan Prestasi di Sekolah Dasar

This study aims to determine the management process conducted by the Principal in improving achievement at Immanuel Christian Elementary School Unit I Pontianak. Data collection techniques such as interviews, direct observations, and documents. Interviews, observations, and documents revealed that school; 1) planning, implementation, and supervision of Principal applied to the principle of consensus, trust, responsibility and kinship, 2) there is a tendency success of Principal in integrating human resources exist, which is arranged in the form of the full cooperation of responsibility so that a force for schools in reaching achievements. Suggestions for school, in this case the citizens of Immanuel Christian Elementary School Unit I Kota Pontianak, in order to improve the quality and academic achievement as well as non-academic achievements. Principal planning program that involves teachers, students, and parents, and implementation, and supervision should be further developed. Besides partnerships with parents and the community which has been established should be improved

Polarization Response in InAs Quantum Dots: Theoretical Correlation between Composition and Electronic Properties

III-V growth and surface conditions strongly influence the physical structure and resulting optical properties of self-assembled quantum dots (QDs). Beyond the design of a desired active optical wavelength, the polarization response of QDs is of particular interest for optical communications and quantum information science. Previous theoretical studies based on a pure InAs QD model failed to reproduce experimentally observed polarization properties. In this work, multi-million atom simulations are performed to understand the correlation between chemical composition and polarization properties of QDs. A systematic analysis of QD structural parameters leads us to propose a two layer composition model, mimicking In segregation and In-Ga intermixing effects. This model, consistent with mostly accepted compositional findings, allows to accurately fit the experimental PL spectra. The detailed study of QD morphology parameters presented here serves as a tool for using growth dynamics to engineer the strain field inside and around the QD structures, allowing tuning of the polarization response.Comment: 8 pages, 6 figures; accepted for publication in IOP Nanotechnology journa

Characteristics of the surface soil ecosystem: Linkage to understanding soil dynamic functions

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Perceived Effects of Adoption of Recommended Practices among Rural Farmers of Nigeria

The study assessed the perceived effects of recommended practices on levels of hygienic practices,health-care Expenditure, and productive time for Agricultural Activities and children school attendances among the rural farmers in Mokwa Local Government area of Niger State, Nigeria. Multi-stage sampling technique was used to select 311 of rural populace. Data were collected using structured questionnaire as well as interview schedule and analyzed using descriptive statistics. The mean age of the respondents was 46 years while the mean household size was 9 persons. Also, the mean years of experience was 20.8 years while 41.4% of the respondents had primary education. The mean household income was Nigerian Naira N175,500.00. The serious constraints to adoption of recommended practices were bad attitude and lack of credit facilities It is recommended that environmental health workers should be empowered to enforce sanctions on noncompliance with adoption of recommended practices and efforts should be made by stakeholders to sustain this channel of sensitization