Explicit Analysis of Sheet Metal Forming Processes Using Solid-Shell Elements

To simulate sheet metal forming processes precisely, an in-house dynamic explicit code was developed to apply a new solid-shell element to sheet metal forming analyses, with a corotational coordinate system utilized to simplify the nonlinearity and to integrate the element with anisotropic constitutive laws. The enhancing parameter of the solid-shell element, implemented to circumvent the volumetric and thickness locking phenomena, was condensed into an explicit form. To avoid the rank deficiency, a modified physical stabilization involving the B-bar method and reconstruction of transverse shear components was adopted. For computational efficiency of the solid-shell element in numerical applications, an adaptive mesh subdivision scheme was developed, with element geometry and contact condition taken as subdivision criteria. To accurately capture the anisotropic behavior of sheet metals, material models with three different anisotropic yield functions were incorporated. Several numerical examples were carried out to validate the accuracy of the proposed element and the efficiency of the adaptive mesh subdivision.

SARS-CoV-2 spike conformation determines plasma neutralizing activity

Numerous safe and effective COVID-19 vaccines have been developed that utilize various delivery technologies and engineering strategies. The influence of the SARS-CoV-2 spike (S) glycoprotein conformation on antibody responses induced by vaccination or infection in humans remains unknown. To address this question, we compared plasma antibodies elicited by six globally-distributed vaccines or infection and observed markedly higher binding titers for vaccines encoding a prefusion-stabilized S relative to other groups. Prefusion S binding titers positively correlated with plasma neutralizing activity, indicating that physical stabilization of the prefusion conformation enhances protection against SARS-CoV-2. We show that almost all plasma neutralizing activity is directed to prefusion S, in particular the S1 subunit, and that variant cross-neutralization is mediated solely by RBD-specific antibodies. Our data provide a quantitative framework for guiding future S engineering efforts to develop vaccines with higher resilience to the emergence of variants and longer durability than current technologies.

PENINGKATAN KEKUATAN TANAH ORGANIK DENGAN PENCAMPURAN EMPAT JENIS LIMBAH RAMAH LINGKUNGAN

Waste is one of the problems in Indonesia. Based on the Ministry of the Environment, each person produces an average of 0.8 kg of waste per day. The average waste per person will increase in line with the increase in people's welfare and lifestyle. Assuming 220 million Indonesians, waste reaches 176,000 tons per day. Accompanied by increasing population growth, the need for infrastructure development on land is increasing. Soils that is often used for construction land is organic soil. It has low soil bearing capacity values and soil improvement methods are commonly used. The general method usually is to mix the soil with better bearing capacity. To minimize costs, a physical stabilization system is carried out that can use soil improvement methods with waste. This can deal with 2 problems at once, where there is the use of certain types of waste and also the planning of organic soil stabilization with small carrying capacity. By doing a triaxial test on organic soil by mixing 4 different types of waste, it shows that the best waste mixture that can affect the bearing capacity of the soil in sequence is coconut husk, tile fragments, construction demolition debris, and chicken egg shells. ABSTRAKLimbah merupakan salah satu permasalahan di Indonesia, Berdasarkan informasi Kementerian lingkungan Hidup, setiap orang menghasilkan rata-rata 0,8 kg sampah per hari. Rata-rata limbah per orang akan meningkat sejalan dengan meningkatnya kesejahteraan dan gaya hidup masyarakat. Dengan asumsi 220 juta penduduk Indonesia, limbah mencapai 176.000 ton per hari. Diiringi dengan peningkatan pertumbuhan penduduk, maka kebutuhan pembangunan infrastruktur di lahan tanah semakin bertambah. Salah satu tanah yang sering dipakai untuk lahan konstruksi adalah tanah organik. Tanah organik memiliki nilai daya dukung tanah yang rendah dan biasa dilakukan metode perbaikan tanah. Metode umum yang biasa dilakukan adalah dengan melakukan pencampuran tanah dengan daya dukung yang lebih baik. Untuk memperkecil biaya maka dilakukannya sistem stabilisasi fisik yang bisa menggunakan metode perbaikan tanah dengan limbah. Hal ini bisa menangani 2 masalah sekaligus, dimana adanya pemanfaatan dari jenis limbah tertentu dan juga perencanaan stabilisasi tanah organik dengan daya dukung kecil. Dengan melakukin uji triaksial pada tanah organik dengan mencampurkan 4 jenis limbah berbeda menunjukan bahwa campuran limbah terbaik yang bisa mempengaruhi daya dukung tanah secara berurutan adalah sabut kelapa, pecahan genteng, puing pembongkaran konstruksi, dan cangkang telur ayam.

Physical stabilization of expansive subgrade soil using locally produced geogrid material

This paper illustrates application of a locally produced geogrid material for strength improvement of expansive subgrade soil. Samples of black, soft soil predominating the study area were collected from south western parts of Modjo town, inside the rift valley region of central parts of Ethiopia. X-Ray diffraction as well as index property tests were executed to identify and categorize the expansiveness of the highly plastic soft soil. The effects of two locally manufactured geogrid reinforcement materials; namely, polypropylene (PP) and high density polyethylene (HDPE) on the California bearing ratio (CBR) values of the expansive soil have been investigated. The test results indicated that the use of the geogrid reinforcement can significantly improve the bearing capacity of weak subgrade soil. The soaked CBR of the untreated soil sample, which was about 2.98%, was able to be raised to 10.16% and 7.48% by the application of PP and HDPE type of geogrid respectively, that were placed at 0.35H from the top of specimen. The research demonstrated the potential of using locally produced geogrid material for the improvement of weak subgrade soil.

Particles under stress: ultrasonication causes size and recovery rate artifacts with soil-derived POM but not with microplastics

The breakdown of soil aggregates and the extraction of particulate organic matter (POM) by ultrasonication and density fractionation is a method widely used in soil organic matter (SOM) analyses. It has recently also been used for the extraction of microplastic from soil samples. However, the investigation of POM physiochemical properties and ecological functions might be biased if particles are comminuted during the treatment. In this work, different types of POM, which are representative of different terrestrial ecosystems and anthropogenic influences, were tested for their structural stability in the face of ultrasonication in the range of 0 to 500 J mL−1. The occluded particulate organic matter (oPOM) of an agricultural and forest soil as well as pyrochar showed a significant reduction of particle size at ≥50 J mL−1 by an average factor of 1.37±0.16 and a concurrent reduction of recovery rates by an average of 21.7±10.7 % when being extracted. Our results imply that increasing ultrasonication causes increasing retention of POM within the sedimenting phase, leading to a misinterpretation of certain POM fractions as more strongly bound oPOM or part of the mineral-associated organic matter (MOM). This could, for example, lead to a false estimation of physical stabilization. In contrast, neither fresh nor weathered polyethylene (PE), polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) microplastics showed a reduction of particle size or the recovery rate after application of ultrasound. We conclude that ultrasonication applied to soils has no impact on microplastic size distribution and thus provides a valuable tool for the assessment of microplastics in soils and soil aggregates.

Thermal Conductivity of CNT - Wated Nanofluids: a Review

In heat transportation applications, water is most commonly used fluid. The efficiency of equipment used in these applications depends on thermal characteristics of water used. The thermal characteristics of water could be upgraded by suspending high thermal conducting solid nanoparticles. In this paper an attempt has been made to know how the use of surfactants and functionalization of carbon nanotube walls can affect the thermal characteristics and stability of nanofluid. A thorough analysis of collected literature revealed that carbon nanotubes have much higher thermal conductivity than any other nanoparticles and hence improve the thermal properties of water when suspended in them. Further it is concluded that suspension of carbon nanotubes in water requires use of surfactant or functionalization of carbon nanotube walls with proper group. By setting optimum pH and better dispersion, better thermal conductivity is possible. Experimental studies in the literature survey reveal that chemical stabilization techniques and physical stabilization techniques together decide the stability of the nanofluid.

Particles under stress: Ultrasonication causes size and recovery rate artifacts with soil derived POM, but not with microplastics

The breakdown of soil aggregates and the extraction of particulate organic matter (POM) by ultrasonication and density fractionation is a method widely used in soil organic matter (SOM) analyses. It has recently also been used for the extraction of microplastic from soil samples. However, the investigation of some POM physiochemical properties and ecological functions might be biased, if particles are comminuted during the treatment. In this work, different types of POM, which are representative for different terrestrial ecosystems and anthropogenic influences, were tested for their structural stability in face of ultrasonication in a range of 0 to 500 J ml−1. The occluded particulate organic matter (oPOM) of an agricultural and forest soil as well as pyrochar showed a significant reduction of particle size at ≥ 50 J ml−1 by an average factor of 1.37 ± 0.16 and a concurrent reduction of recovery rates by an average of 21.7 ± 10.7 % when being extracted. Our results imply that ultrasonication causes an imitated carry-over of POM to more strongly bound fractions or to the mineral-associated organic matter (MOM) due to enhanced attraction to the mineral phase, which could e.g. lead to a false estimation of physical stabilization. In contrast, neither fresh nor weathered polyethylene (PE), polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) microplastics showed a reduction of particle size or the recovery rate after application of ultrasound. We conclude that ultrasonication applied to soils has no impact on microplastic size distribution and thus provides a valuable tool for the assessment of microplastics in soils and soil aggregates.

Organic Matter of Cultural Layers as a Material for Radiocarbon Dating

ABSTRACTThis article focuses on radiocarbon (14C) dating of the organic matter (OM) of natural-anthropogenic objects—the cultural layers (CLs) of archaeological sites. Using examples from three ancient sites located within the European part of Russia, in southern taiga and forest-steppe natural zones, we demonstrate approaches to the interpretation of 14C dating of OM derived from the organomineral material of the CLs studied. We use the term “archaeological humus” as defined as the OM formed within the CL from “anthropogenic matter” (i.e., organic residues that were produced during the past human occupation of the site) without or with negligible contribution of OM inherited from pre-anthropogenic stages of pedogenesis. The archaeological humus is formed within closed or semi-closed systems by the processes of humification and physical stabilization of OM. The use of hierarchical (from macro- to submicro-) morphological investigations at one of the sites (Gnezdovo) combined with 14C dating allowed conclusions to be drawn about the age of formation of different OM components in CLs.