Investigation of Aluminum-Stainless Steel Dissimilar Weld Quality using Different Filler Metals

Aluminum-stainless steel dissimilar welding processes yield unwanted disadvantages in the weld joint due to the large difference between the aluminum-stainless steel sheets’ melting points and the nearly zero solid solubility between these two metals. Aluminum AA6061 and stainless steel SUS304 were lap-welded by using Metal Inert Gas (MIG) welding with aluminum filler ER5356 (Group 1) and stainless steel filler ER308LSi (Group 2). The effects of the welding voltage and type of filler metals used on the weld joints were studied. The welding voltage had a significant effect on the welding process, as higher voltage resulted in poorer appearance of the weld joint and led to defects for both groups, such as porosity and incomplete fusion. The microstructure for Group 1 joints shows enrichment of Si particles, which benefited the joint properties as it increased the strength of the metal. The stainless steel substrates that spread into the aluminum side are much greater in volume for Group 1 than for Group 2 joints. Meanwhile, the microstructure of Group 2 joints (using ER308LSi filler) consists of chromium carbide precipitation which yields a high hardness value, but a brittle structure. The hardness values of the welded seams in Group 1 and Group 2 range from 60 to 100 HV and 160 to 230 HV, respectively. The fracture in the tensile test yielded the highest tensile strength of 104.4 MPa with aluminum fillers. The tensile strength of Group 1 joints ranging from 47.8 to 104.4 MPa was collectively higher than Group 2 joints, between 20.24 to 61.76 MPa. Based on the investigation throughout this study, it can be concluded that the welding voltage of 18 V and aluminum filler ER5356 is the optimum filler in joining the dissimilar metals aluminum AA6061 and stainless steel SUS 304

Analisis Persepsi Jasa Pelayanan Pendidikan dengan Menggunakan Model Kano dan IPA pada Perguruan Xyz

Pihak manajemen sekolah XYZ selalu berusaha memenuhi kebutuhan murid dengan melakukan perbaikan secara berkesinambungan untuk memberikan pelayanan yang lebih baik kepada siswa. Pada penelitian ini, tingkat kepuasan dan persepsi siswa diteliti guna mengetahui atribut pelayanan yang menjadi prioritas untuk ditingkatkan oleh pihak manajemen sekolah dari 25 atribut pelayanan yang tersedia. Metode Importance Performance Analysis (IPA) digunakan untuk mengetahui persepsi siswa terhadap pelayanan sekolah. Importance Performance Analysis menunjukkan delapan atribut yang memiliki tingkat kepentingan tertinggi sehingga perlu diperhatikan oleh pihak manajemen sekolah. Metode KANO digunakan untuk mengidentifikasi tingkat kepuasan dan ketidakpuasan dari masing-masing atribut. Matriks kepuasan dan ketidakpuasan pada metode KANO menunjukkan enam atribut dengan tingkat kepuasan dan ketidakpuasan tertinggi sehingga perlu menjadi perhatian pihak manajemen sekolah. Integrasi KANO dan IPA digunakan untuk menentukan atribut yang menjadi prioritas dalam perbaikan yang dapat dilakukan oleh pihak manajemen sekolah. Hasil penelitian menunjukkan adanya tiga atribut prioritas yaitu kemampuan guru merespon pertanyaan siswa, kemampuan guru memberikan pedoman hidup kepada siswa, dan kemampuan guru memberikan informasi tentang masa depan kepada siswa. Ketiga atribut yang menjadi prioritas perbaikan dapat ditingkatkan dengan memberikan pelatihan ataupun seminar mengenai pendidikan dan teknologi pendidikan kepada guru, melakukan pertukaran guru dari dalam sekolah dengan guru dari sekolah-sekolah lain dan memberikan kesempatan studi banding kepada guru untuk memperluas wawasan mereka

Mechanical Strength Of Dissimilar AA7075 and AA6061 Aluminum Alloys Using Friction Stir Welding

The present study focuses on the effects of material position and tool rotational speed on the tensile strength of dissimilar AA7071 and AA6061 welded aluminum alloys with a thickness of 2.0 mm in using a conventional milling machine. Ten joints were produced by varying tool rotational speeds and by changing the fixed position of the material on the advancing and retreating sides. The results show that the maximum tensile strength of 207 MPa was achieved for Sample E when AA6061 aluminum alloys were placed on the advancing side at a rotational speed of 1000 rpm with seamless surface appearance and no inner defect across the weld area, while the lowest tensile strength of 160 MPa was obtained for Sample F when AA6061 was placed on the retreating side with severe tunnel defects across the weld area contributing to crack propagation. Thus, in dissimilar welding, weaker materials should be placed on the advancing side to trigger heat from the tool rotation and smooth the material flow formation in the stirred zone

Upaya Pencegahan Gigitan Nyamuk dengan Keberadaan Kasus Malaria

Setiap tahun lebih dari 500 juta penduduk dunia terinfeksi malaria dan lebih dari satu juta orang meninggal dunia. Penelitian bertujuan mengetahui hubungan penggunaan kelambu, pemasangan kawat kasa, penggunaan obat nyamuk, penggunaan repellent saat keluar rumah pada malam hari, pemakaian baju lengan panjang saat keluar rumah pada malam hari dengan keberadaan kasus malaria di wilayah kerja Puskesmas Bonto Bahari Kabupaten Bulukumba. Jenis penelitian yang digunakan adalah observasional dengan rancangan cross sectional study. Populasi adalah 8.199 KK yang berada di wilayah kerja Puskesmas Bonto Bahari. Sampel penelitian ini sebanyak 181 KK dengan menggunakan teknik proporsional random sampling. Analisis data yang dilakukan adalah univariat dan bivariat dengan uji chi square. Hasil penelitian diperoleh variabel yang berhubungan dengan keberadaan kasus malaria adalah penggunaan obat nyamuk (p=0,001). Variabel yang tidak berhubungan dengan keberadaan kasus malaria adalah penggunaan kelambu (p=0,605), pemasangan kawat kasa (p=0,461), penggunaan repellent saat keluar rumah pada malam hari (p=0,461), pemakaian baju lengan panjang saat keluar rumah pada malam hari (p=0,988). Kesimpulan dari penelitian bahwa ada hubungan penggunaan obat nyamuk dengan keberadaan kasus malaria di wilayah kerja Puskesmas Bonto Bahari Kabupaten Bulukumba tahun 2014.Kata kunci : Pencegahan gigitan nyamuk, malari

The Tolman VII solution, trapped null orbits and w - modes

The Tolman VII solution is an exact static spherically symmetric perfect fluid solution of Einstein's equations that exhibits a surprisingly good approximation to a neutron star. We show that this solution exhibits trapped null orbits in a causal region even for a tenuity (total radius to mass ratio) $> 3$. In this region the dynamical part of the potential for axial w - modes dominates over the centrifugal part.Comment: 5 pages revtex. 10 figures png. Further information at http://grtensor.phy.queensu.ca/tolmanvii

Effect of hydrophilic coating for membrane assisted air diffuser for Chlorella vulgaris cultivation

Microalgae cultivation has high potential in capturing atmospheric carbon dioxide (CO2) but are limited by poor CO2 mass transfer to the algae. Therefore, improving mass transfer by increasing total contact area of gas-liquid through minimizing bubble size formed is investigated. In this project, the effect of polyether block amide (PEBAX® 1657) coating (i.e. different concentration and coating cycle) on polyvinylidenefluoride (PVDF) membrane surface properties are investigated and their impact on algae cultivation are evaluated using Chlorella vulgaris for duration of 14 days. The presence of functional groups from PEBAX coating showed the success of coating process and membrane hydrophilicity is improved from 111.19 ± 0.10° to 40.57 ± 1.29° when PEBAX 2.0 wt% is used. Membrane porosity is reduced when PEBAX concentration and number of coating cycle increased. Concentration of biomass is the highest (1.107 g/L) when PVDF/PEBAX 2.0 wt% is used, likely because of small size of CO2 bubbles delivered into culture medium

The growth of structure in the Szekeres inhomogeneous cosmological models and the matter-dominated era

This study belongs to a series devoted to using Szekeres inhomogeneous models to develop a theoretical framework where observations can be investigated with a wider range of possible interpretations. We look here into the growth of large-scale structure in the models. The Szekeres models are exact solutions to Einstein's equations that were originally derived with no symmetries. We use a formulation of the models that is due to Goode and Wainwright, who considered the models as exact perturbations of an FLRW background. Using the Raychaudhuri equation, we write for the two classes of the models, exact growth equations in terms of the under/overdensity and measurable cosmological parameters. The new equations in the overdensity split into two informative parts. The first part, while exact, is identical to the growth equation in the usual linearly perturbed FLRW models, while the second part constitutes exact non-linear perturbations. We integrate numerically the full exact growth rate equations for the flat and curved cases. We find that for the matter-dominated era, the Szekeres growth rate is up to a factor of three to five stronger than the usual linearly perturbed FLRW cases, reflecting the effect of exact Szekeres non-linear perturbations. The growth is also stronger than that of the non-linear spherical collapse model, and the difference between the two increases with time. This highlights the distinction when we use general inhomogeneous models where shear and a tidal gravitational field are present and contribute to the gravitational clustering. Additionally, it is worth observing that the enhancement of the growth found in the Szekeres models during the matter-dominated era could suggest a substitute to the argument that dark matter is needed when using FLRW models to explain the enhanced growth and resulting large-scale structures that we observe today (abridged)Comment: 18 pages, 4 figures, matches PRD accepted versio

Dynamical dark energy: Current constraints and forecasts

We consider how well the dark energy equation of state $w$ as a function of red shift $z$ will be measured using current and anticipated experiments. We use a procedure which takes fair account of the uncertainties in the functional dependence of $w$ on $z$, as well as the parameter degeneracies, and avoids the use of strong prior constraints. We apply the procedure to current data from WMAP, SDSS, and the supernova searches, and obtain results that are consistent with other analyses using different combinations of data sets. The effects of systematic experimental errors and variations in the analysis technique are discussed. Next, we use the same procedure to forecast the dark energy constraints achieveable by the end of the decade, assuming 8 years of WMAP data and realistic projections for ground-based measurements of supernovae and weak lensing. We find the $2 \sigma$ constraints on the current value of $w$ to be $\Delta w_0 (2 \sigma) = 0.20$, and on $dw/dz$ (between $z=0$ and $z=1$) to be $\Delta w_1 (2 \sigma)=0.37$. Finally, we compare these limits to other projections in the literature. Most show only a modest improvement; others show a more substantial improvement, but there are serious concerns about systematics. The remaining uncertainty still allows a significant span of competing dark energy models. Most likely, new kinds of measurements, or experiments more sophisticated than those currently planned, are needed to reveal the true nature of dark energy.Comment: 24 pages, 20 figures. Added SN systematic uncertainties, extended discussio

All static spherically symmetric perfect fluid solutions of Einstein's Equations

An algorithm based on the choice of a single monotone function (subject to boundary conditions) is presented which generates all regular static spherically symmetric perfect fluid solutions of Einstein's equations. For physically relevant solutions the generating functions must be restricted by non-trivial integral-differential inequalities. Nonetheless, the algorithm is demonstrated here by the construction of an infinite number of previously unknown physically interesting exact solutions.Comment: Final form to appear in Phys Rev D. Includes a number of clarification

The mechanical performance of sugar palm fibres (Ijuk) reinforced phenolic composites

Sugar palm fibres are one of the natural fibres which have many features and need further study to understand their properties. The aim of this work is to investigate the flexural, compressive and impact properties of sugar palm fibres reinforced phenolic composites. Sugar palm fibres were used as a filler (particle size 150 μm) and with loading of 0, 10, 20, 30, and 40 vol.%. The fibres were treated by sea water and then fabricated into composites by hot press technique. Flexural, compressive, and impact tests were carried out as per ASTM D790, ASTM D695-08a, and ASTM D256 standards, respectively. Scanning electron microscopy (SEM) was used to investigate the morphology and the interfacial bonding of the fibres-matrix in composites. The results show that the mechanical properties of the composites improve with the incorporation of fibres. The composite of 30 vol.% particle loading exhibit optimum values which are 32.23 MPa, 61.66 MPa, and 4.12 kJ/m2 for flexural, compressive, and impact strength, respectively. This was because good compatibility of fibre-matrix bonding. Consequently, sugar palm fibre is one of the prospective fibres and could be used as a potential resource to reinforcement polymer composite