Pemanfaatan Bahan Alam Anchor sebagai Bahan Konservasi Fosil di Sangiran

Balai Pelestarian Situs Manusia Purba Sangiran telah menggunakan bahan alam anchor sebagai bahan perekat untuk menyambungkan fosil yang patah sejak tahun 2018 setelah melakukan penelitian selama dua tahun yaitu pada tahun 2016 dan pada tahun 2017. Seiring berjalannya waktu penggunaan bahan alam anchor mengalami kerusakan seperti hasil sambungan patah atau retak yang diakibatkan penyimpanan fosil yang kurang tepat. Penelitian ini bertujuan untuk menentukan kekuatan mekanik campuran fosil dan anchor. Penelitian menggunakan rancangan acak lengkap satu faktor dengan variasi perbandingan fosil ukuran 100mesh dan anchor (1:1, 2:1, dan 3:1) dengan dua ulangan. Kemudian melakukan pengujian kuat tekan menggunakan universal testing machine berdasarkan standar ASTM D695-96. Hasilnya menunjukkan nilai kuat tekan tertinggi campuran serbuk fosil dan anchor dengan pada perbandingan 1:1 yaitu 19,996 N/mm2 dan nilai kuat tekan terendah pada perbandingan serbuk fosil dan anchor 3:1 yaitu 12,51 N/mm2. Lem anchor hasil penelitian telah memenuhi persyaratan SNI 06-6049-1999 tentang polivinil asetat emulsi untuk pengerjaan kayu sebagai standar pembanding yaitu memiliki kekuatan rekat minimal 3 N/mm2 dan memiliki pH (3-8).

Fracture Resistance of Primary Zirconia Crowns: An In Vitro Study

In this study, we evaluated the fracture resistance of three commercially available prefabricated primary zirconia crowns and their correlation with dimensional variance. Methods: a total of 42 zirconia crowns were selected from three companies, (1) NuSmile primary zirconia crowns, (2) Cheng Crowns zirconia, and (3) Sprig EZ crowns. The crowns were divided into two groups based on their location in the oral cavity and further divided into subgroups based on the brand. All of the samples were subjected to fracture tests using a universal testing machine. Results: the mean load observed was highest with Cheng Crowns zirconia anterior crowns (1355 ± 484) and the least load was seen with Sprig EZ anterior crowns with a mean load of 339 ± 94. The mean load observed was highest with Cheng Crowns zirconia posterior crowns (1990 ± 485) followed by NuSmile posterior crowns and the least load was seen with Sprig EZ posterior crowns with a mean load of 661 ± 184. Conclusion: the Cheng crowns showed the highest fracture resistance amongst all three groups. Overall, the zirconia crowns (anterior and posterior) tested showed optimum mechanical properties to withstand the masticatory forces.

Contriving and Assessment of Magnesium Alloy Composites Augmented with Boron Carbide VIA Liquid Metallurgy Route

In modern engineering low-density composites plays a vital role of which magnesium alloys are very effective due to its high strength with better corrosion resistance and neat cast ability. In this work a micron sized Boron carbide ceramic (B4C) of about 100 microns is diffused as a reinforcement with AZ91 for preparing a magnesium metal matrix composite (MMMC) through stir casting route. A modified pit furnace setup is used for doing stir casting with varying volume fractions of 0％ and 3% of boron carbide for doing the composites. Furthermore mechanical and metallurgical properties like Tensile test is made through universal testing machine, Micro-hardness through Vickers hardness tester and Micro structure through Optical Microscopy is done for investigation.

Identifikasi material dan perhitungan kembali tegangan tangensial barrel rear suspension dump truck EH 5000

Suspensi dump truck berfungsi sebagai peredam kejutan dari permukaan jalan, penyangga berat unit, memberikan kenyamanan pada operator dan menjaga kestabilan unit (empat roda selalu menyentuh tanah). Barrel adalah komponen penting dalam suspensi dump truck. Komponen tersebut berbentuk tabung pada suspensi dan berfungsi sebagai rumah untuk piston. Barrel yang bukan standar original Hitachi sering mengalami kerusakan. Penelitian ini bertujuan untuk mengetahui nilai kekerasan dan kekuatan tarik pada material barrel suspensi belakang, komposisi kimia dan struktur mikro pada material barrel suspensi belakang, dan nilai tegangan tangensial pada dinding barrel.Penelitian ini dilakukan dengan empat pengujian, yaitu uji kekerasan, uji tarik, uji struktur mikro dan uji komposisi kimia. Pengujian kekerasan dengan menggunakan alat uji kekerasan Brinell, pengujian tarik dengan menggunakan alat uji tarik (universal testing machine), pengujian komposisi kimia dengan alat spectrometer, dan pengujian struktur mikro dengan metallographic microscope. Sedangkam untuk mencari nilai tegangan pada dinding barrel dilakukan perhitungan tegangan tangensial.Hasil dari penelitian ini menunjukkan bahwa material barrel mempunyai nilai kekerasan rata rata 200,50 HB, nilai kekuatan luluh σy 433-494 MPa, nilai kekuatan tarik σu 740-751 MPa, kandungan pada material termasuk kategori baja 27 SiMn, struktur mikro pada material terdapat fasa ferrite dan pearlite, material aman terhadap beban statis, dan tegangan tangensial yang terjadi lebih rendah dari kekutan luluh.

Influence of Geometry in the Behavior of Disc-Shaped Mechanical Energy Absorbers for Agricultural Tractors

Disc-shaped mechanical energy absorbers (MEAs), in combination with rollover protection structures (ROPSs), may contribute to the prevention of the infringement of the safety zone and the collapse of the ROPS in case of the overturn of an agricultural tractor. An MEA can absorb a significant amount of potential energy of an overturning tractor and its deformation produces a rotation of the ROPS around the safety zone. In this research, MEAs with two different geometries have been developed. Both geometries present common features, such as disc dimensions, number of rings, and number of arms, but the distribution of the arms differs. Additionally, these MEA were manufactured in steel discs of four different thicknesses, ranging from 2 to 6 mm. The manufactured MEAs were tested in a universal testing machine, and their behavior characterized. From this data, linear models of the MEAs were developed. As a consequence, a number of characteristic parameters were selected and calculated, such as the activation load and the strain energy absorbed in a safe range of applied loads. Some patterns and trends were analyzed from the tested MEAs, which enables a better description of their behavior and the extrapolation of this behavior to other non-tested thicknesses and geometries.

Effect of Compressive Strain Rate on Microstructure and Mechanical Properties of 7050 Aluminium Alloy

7050 aluminium alloy is a superior material used in the areas of aerospace and automobile manufacturing. In this work, homogeneous cast cylinder samples of 7050 aluminium alloy with size of Φ80 mm × 100 mm were compressed isothermally at 350°C with compressive strain rate of 0.1 s−1,1 s−1, and 10 s−1, respectively. The samples were then processed into standard tensile specimens, and then tensile testing was done by using the GL8305 universal testing machine. The grain sizes and fracture morphology were analyzed by the SEM observation and cellular automaton (CA) method. The effect of compressive strain rate on microstructure and mechanical properties of 7050 aluminium alloy was investigated. The results show the following. (1) Grain refinement occurred after compression. The grain sizes of the samples decrease with the decrease of compressive strain rate. The grain sizes in the radial edge and the axial center of the cylinder samples are the smallest. (2) The tensile strength and breaking elongation rate were improved when compared to the original alloy. The mechanical properties of samples compressed with compressive strain rate of 0.1 s−1 are the best. (3) The fracture morphology of the samples shows that the fracture of the samples is ductile fracture. The sizes and depths of dimples increased with the decrease of grain sizes.

Manufacture and Characterization of Alginate-CMC-Dextran Hybrid Double Layer Superabsorbent Scaffolds

This study focused on the manufacturing of functional superabsorbent sponges using natural polymers. An alginate/CMC-embedded dextran hybrid dual-layer formulation was prepared using the freeze-drying method. The physical properties of the formulation were characterized using a field emission scanning electron microscope and a universal testing machine, and the swelling ratio was calculated. Cell viability assays were performed using keratinocytes (HaCaT cells). The results showed that this formulation can absorb a large amount of moisture and provide morphological stability through its tensile strength and uniform porosity, and this was verified by its biocompatibility. We believe that in the future, by combining this novel hybrid dual-layer superabsorbent sponge with antibacterial agents with excellent porosity, it would serve as a medical material for producing bandages that can absorb blood and body fluids, feminine hygiene products, and functional antibacterial masks.

Investigation of Single Fibre Tensile Properties of the Pineapple Leaf (PALF)

Recently, natural fibres composite is rigorously explored as alternative fibres due to the source depletion of petroleum. This research was focusing on pineapple leaf (PALF). The purpose of this research was to study the single fibre tensile properties of PALF. The single fibre tensile test was conducted via the universal testing machine following ASTM D3379 – 89 standards. The result shows that the Ultimate Tensile Strength (UTS) and Young’s Modulus of PALF were 141.093 MPa and 89.073 MPa, respectively. This research’s benefits include reducing agriculture waste of pineapple leaf, which is commonly being thrown out by the farmers when the fruits are harvested. It focuses not only on waste reduction but also on economic factors when other industries fully utilise the pineapple leaf.

Monitoring for COVID-19 by universal testing in a homeless shelter in Germany: a prospective feasibility cohort study

Background Living conditions in homeless shelters facilitate the transmission of COVID-19. Social determinants and pre-existing health conditions place homeless people at increased risk of severe disease. Described outbreaks in homeless shelters resulted in high proportions of infected residents and staff members. In addition to other infection prevention strategies, regular shelter-wide (universal) testing for COVID-19 may be valuable, depending on the level of community transmission and when resources permit. Methods This was a prospective feasibility cohort study to evaluate universal testing for COVID-19 at a homeless shelter with 106 beds in Berlin, Germany. Co-researchers were recruited from the shelter staff. A PCR analysis of saliva or self-collected nasal/oral swab was performed weekly over a period of 3 weeks in July 2020. Acceptability and implementation barriers were analyzed by process evaluation using mixed methods including evaluation sheets, focus group discussion and a structured questionnaire. Results Ninety-three out of 124 (75%) residents were approached to participate in the study. Fifty-one out of the 93 residents (54.8%) gave written informed consent; thus 41.1% (51 out of 124) of all residents were included in the study. Among these, high retention rates (88.9–93.6%) of a weekly respiratory specimen were reached, but repeated collection attempts, as well as assistance were required. Around 48 person-hours were necessary for the sample collection including the preparation of materials. A self-collected nasal/oral swab was considered easier and more hygienic to collect than a saliva specimen. No resident was tested positive by RT-PCR. Language barriers were the main reason for non-participation. Flexibility of sample collection schedules, the use of video and audio materials, and concise written information were the main recommendations of the co-researchers for future implementation. Conclusions Voluntary universal testing for COVID-19 is feasible in homeless shelters. Universal testing of high-risk facilities will require flexible approaches, considering the level of the community transmission, the available resources, and the local recommendations. Lack of human resources and laboratory capacity may be a major barrier for implementation of universal testing, requiring adapted approaches compared to standard individual testing. Assisted self-collection of specimens and barrier free communication may facilitate implementation in homeless shelters. Program planning must consider homeless people’s needs and life situation, and guarantee confidentiality and autonomy.