Molecular-dynamic Investigation of Silicon Carbide Fracture Under External Mechanical Loads

In this study, molecular dynamic simulations of quasi-static compression of silicon carbide nanorod, were performed. A longitudinal through defect in the form of a cylindrical channel was in- troduced into the central part of the nanorod. The influence of the cross sectional size of this internal channel on the strength properties was investigated

Simulasi ETAP 12.6 untuk Studi Instalasi Listrik pada Kereta Api Kahuripan

AbstrakDalam sebuah satu rangkaian kereta biasanya terdiri dari penggerak utama lokomotif, kereta penumpang, kereta makan, dan kereta pembangkit. Dengan banyaknya fasilitas dan alat-alat kelistrikan dalam gerbong-gerbong tersebut dapat memberikan dampak penurunan terhadap kualitas daya listrik yang mengalir pada sistem distribusi aliran daya. Penelitian ini bertujuan untuk mengetahui kapasitas nilai circuit breaker, ukuran penampang kabel, tegangan jatuh, dan rugi-rugi daya, serta perbandingangannya dengan hasil simulasi pada software ETAP 12.6. Kapasitas circuit breaker dan ukuran penampang kabel yang diperhitungkan mendapatkan rating circuit breaker dengan arus berkisar dari 800 hingga 80 Ampere dan ukuran kabel yang digunakan sebesar 120 mm2. Hasil nilai drop voltage yang didapat dimulai dari 1,02 Volt hingga 5,08 Volt. Untuk nilai rugi-rugi daya yang didapat dimulai dari dari 0,01 kW hingga 0,11 kW.Kata kunci: Aliran Beban, ETAP, Circuit Breaker, Drop Voltage, Rugi-rugi Daya.AbstractA train usually consists of several carrieges: a prime mover locomotive, passenger carriage, dining carriage, and generator carriage. With that many facilities and installed electrical equipments the quality of the electric power flowing in the trains’s power distribution system may be decresed. This study aims to determine the capacity of the circuit breaker, the cable’s cross section size, the voltage drop, and power losses, as well as the comparison with the simulation results by using ETAP software. The circuit breaker capacity and cable’s cross-sectional size are calculated. From the calculations, we obtain the rating value for the circuit breaker, which is ranging from 800 to 80 Ampere. As for the cable’s corss sectional we obtain 120 mm2. With these values, the resulting voltage drop is from 1.02 Volts to 5.08 Volts. As for the resulting power loss, its value is ranging from 0.01 kW to 0.11 kW.Keywords: Load Flow, ETAP, Circuit Breaker, Voltage Drop, Power Loss.

Analisis Terjadinya Arus Netral Pada Trafo Distribusi 160 kVA

The Power distribution in a 3-phase system, cannot be separated from the flow of current in the neutral of the transformer, which will cause power losses (losses) where current flows into the neutral conductor and losses that flow into the neutral conductor. This study was conducted to determine the causes and magnitude of power losses that occur due to the occurrence of neutral current flowing in the neutral conductor in a 160kVA distribution transformer. The research location taken is the Distribution Transformer (G187 T) which is located on Jl. Hos Cokroaminoto Wisma Ombilin where load imbalances often occur. From the results, it can be seen that if the neutral wire has a cross-sectional size of 50 mm2, the current that passes through the neutral wire is 6.4% for the day and for the cross-sectional size of the wire is 70 mm2, it can reduce the power flowing to the neutral by a percentage of 4.77%. for the daytime. Efficiency value that occurs is greater at night that is 94.87% while for the day it is 93.44%. For the distribution of each - each phase, especially the S phase, so that it can be balanced because the power supplied to the S phase is too small. We recommend that the current flowing in the neutral wire must be channeled to the ground so that the current flowing in the neutral wire becomes zero.

In silico biomechanical design of the metal frame of transcatheter aortic valves: multi-objective shape and cross-sectional size optimization

Transcatheter aortic valve (TAV) implantation has become an established alternative to open-hearth surgical valve replacement. Current research aims to improve the treatment safety and extend the range of eligible patients. In this regard, computational modeling is a valuable tool to address these challenges, supporting the design phase by evaluating and optimizing the mechanical performance of the implanted device. In this study, a computational framework is presented for the shape and cross-sectional size optimization of TAV frames. Finite element analyses of TAV implantation were performed in idealized aortic root models with and without calcifications, implementing a mesh-morphing procedure to parametrize the TAV frame. The pullout force magnitude, peak maximum principal stress within the aortic wall, and contact pressure in the left ventricular outflow tract were defined as objectives of the optimization problem to evaluate the device mechanical performance. Design of experiment coupled with surrogate modeling was used to define an approximate relationship between the objectives and the TAV frame parameters. Surrogate models were interrogated within a fixed design space and multi-objective design optimization was conducted. The investigation of the parameter combinations within the design space allowed the successful identification of optimized TAV frame geometries, suited to either a single or groups of aortic root anatomies. The optimization framework was efficient, resulting in TAV frame designs with improved mechanical performance, ultimately leading to enhanced procedural outcomes and reduced costs associated with the device iterative development cycle.

Tumor innervation and clinical outcome in pancreatic cancer

Pancreatic cancer is a highly aggressive malignancy characterized by poor survival, recurrence after surgery and resistance to therapy. Nerves infiltrate the microenvironment of pancreatic cancers and contribute to tumor progression, however the clinicopathological significance of tumor innervation is unclear. In this study, the presence of nerves and their cross-sectional size were quantified by immunohistochemistry for the neuronal markers S-100, PGP9.5 and GAP-43 in a series of 99 pancreatic cancer cases versus 71 normal adjacent pancreatic tissues. A trend was observed between the presence of nerves in the tumor microenvironment of pancreatic cancer and worse overall patient survival (HR = 1.8, 95% CI 0.77–4.28, p = 0.08). The size of nerves, as measured by cross-sectional area, were significantly higher in pancreatic cancer than in the normal adjacent tissue (p = 0.002) and larger nerves were directly associated with worse patient survival (HR = 0.41, 95% CI 0.19–0.87, p = 0.04). In conclusion, this study suggests that the presence and size of nerves within the pancreatic cancer microenvironment are associated with tumor aggressiveness.

A model of developmental canalization, applied to human cranial form

Developmental mechanisms that canalize or compensate perturbations of organismal development (targeted or compensatory growth) are widely considered a prerequisite of individual health and the evolution of complex life, but little is known about the nature of these mechanisms. It is even unclear if and how a “target trajectory” of individual development is encoded in the organism’s genetic-developmental system or, instead, emerges as an epiphenomenon. Here we develop a statistical model of developmental canalization based on an extended autoregressive model. We show that under certain assumptions the strength of canalization and the amount of canalized variance in a population can be estimated, or at least approximated, from longitudinal phenotypic measurements, even if the target trajectories are unobserved. We extend this model to multivariate measures and discuss reifications of the ensuing parameter matrix. We apply these approaches to longitudinal geometric morphometric data on human postnatal craniofacial size and shape as well as to the size of the frontal sinuses. Craniofacial size showed strong developmental canalization during the first 5 years of life, leading to a 50% reduction of cross-sectional size variance, followed by a continual increase in variance during puberty. Frontal sinus size, by contrast, did not show any signs of canalization. Total variance of craniofacial shape decreased slightly until about 5 years of age and increased thereafter. However, different features of craniofacial shape showed very different developmental dynamics. Whereas the relative dimensions of the nasopharynx showed strong canalization and a reduction of variance throughout postnatal development, facial orientation continually increased in variance. Some of the signals of canalization may owe to independent variation in developmental timing of cranial components, but our results indicate evolved, partly mechanically induced mechanisms of canalization that ensure properly sized upper airways and facial dimensions.

Stress Loss of Pre-Tensed CFRP Strips Strengthening Square RС Column

Pre-tensing the CFRP strip strengthening RC column can improve the strain lag of the confined concrete and avoid unloading of column in advance. The pre-stress of strip has an important influence of strengthen. Stress loss of the strip pre-tensed by using the device proposed were investigated by using an experimental test. Firstly, the reasons for the stress loss of strip were analyzed according to the working principle of the device and the strengthening procedure. Then the primary causes of the stress loss, such as friction, relaxation and removing device, were experimentally tested. The influence of the pretension, detail and sectional geometric dimension on the stress loss of the strip were studied. The results show that all three types of pre-stress losses increase significantly with the initial stress. Increasing the cross-sectional size would reduce the relaxation and unwinding losses, but it has little effect on friction losses. The influence of fillet radius on the pre-stress loss was negligible, but in order to avoid premature tearing of local CFRP caused by stress concentration, the chamfer should be made as large as possible within the thickness of concrete protective cover. The test also found that friction was the main cause of stress loss, and friction loss accounts for more than 90% of the total loss.

Failure Analysis of Glulam Lumber Beam Made from Meranti Lumber Pieces (Shorea SP)

The development of glue-laminated (glulam) lumber beam gives many good results. Meranti (Shorea SP) is one of the construction lumber that can be used as glulam to optimize its use. The limitation of the glulam lumber beam is the limited length of the lumber, so it must be joined to get a certain length. The lumber available in the market on average has a limited size and cross-sectional length. The larger the cross-sectional size and length of the lumber make the higher the price. Used lumber and residual lumber also have many weaknesses, such as the length of suitable lumber is too short, lumber defects, and lumber damages. Further research needs to be done to optimize the use of new, used, and residual meranti lumber through the use of lumber pieces as a glulam lumber beam maker. Standard specimen and test based on ASTM D-198. Glulam lumber beam is made from pieces of meranti lumber planks of certain length which are arranged into lamina beam with the size of 5.5x9.5x150 cm3. Variations in the length of the pieces of meranti lumber planks for making glulam lumber beam, among others, 40 cm, 50 cm, 60 cm, 50 cm with full length lowest layer and 150 cm (full length). The adhesive used is polyurethane glue. The span between supports is 130 cm. The beam is tested for center point loading. The analysis results show that the joints on the outermost layer that receive tensile stress of the glulam lumber beam can cause weakening in the beam because the tensile strength of the adhesive is weaker than the tensile strength of lumber. Failure at the tensile joint of the outer layer of the beam can trigger a shear failure mode. Design of joints should not be placed on layers that are subject to tensile stresses so as not to trigger shear failure modes so that the strength of the glulam lumber beam can be optimal.