Safety Margin Research Articles

The Use of the Galea Flap for the Reconstruction of Forehead Defects

The forehead, a vital anatomical unit of the face, is delimited by the anterior hairline superiorly and by the nasal root, eyebrows, and a horizontal line through the lateral canthus inferiorly. Malignant tumors like basal cell carcinomas frequently afflict this region, necessitating meticulous reconstruction techniques to preserve aesthetics and functionality. This article presents an in-depth exploration of the galea flap graft’s efficacy in addressing tissue defect on the forehead, especially in cases of basal cell carcinomas. The surgical procedure involves a wide excision with a 1 cm safety margin, including the frontal muscle and periosteum, followed by exposing the frontal bone. A meticulous approach is taken in tracing the midline, marking the hairline, and planning the left hemi coronal incision to ensure optimal outcomes. The galea flap, vascularized by branches of the superficial temporal artery, is meticulously lifted and transposed downwards to cover the tissue defect, while ensuring the viability of the flap. Postoperative monitoring reveals no signs of cutaneous or vascular damage, with preserved sensory and motor functions attributed to the preservation of the frontal branch of the facial nerve. The discussion delves into the intricate anatomy of the forehead, emphasizing its vascularization, innvervation, and aesthetic subunits such as the glabella and eyebrows. Various surgical techniques, including direct suturing, directed healing, skin grafts, advancement flaps, and two-stage scalp flaps, are examined in light of their efficacy and limitations in forehead reconstruction. The galea flap emerges as a preferred option due to its reliable vascular supply, ease of lifting, and versatility in covering tissue defects while preserving aesthetics. Future research directions are suggested, focusing on refining surgical techniques to achieve optimal outcomes in forehead tissue reconstruction, balancing esthetic results with functional integrit.

Inhaled methoxyflurane - an explorable alternative to nitrous oxide?

Nitrous oxide is a widely used and well-established form of inhalation sedation in dentistry. Its properties have a wide margin of safety and allow for anxious, paediatric and adult patients to receive dental treatment with minimal impact upon discharge. Nitrous oxide has drawbacks, however, including its environmental impact and need for specialist equipment. Methoxyflurane is another drug which could prove to be an alternative to nitrous oxide. Methoxyflurane's use has proved popular within emergency medicine in Australia and New Zealand for its potent analgesic effects and recognition of its anxiolytic effect. As a result, its use in invasive outpatient procedures has now become popular. Unfortunately, there is very limited evidence of its use within dentistry as a form of inhalation sedation and analgesic. A wider evidence base should be established, as methoxyflurane could prove to be an effective and environmentally friendly alternative to nitrous oxide.

Smart management of pressure regulating stations to maximize hydrogen injection in a gas distribution network

Gas distribution networks traditionally maintain constant pressure setpoints at regulating stations, ensuring a consistent supply to end-users with a high safety margin. However, the prospect of hydrogen injection in the gas networks necessitates rethinking operational strategies. This study examines the environmental and fluid-dynamic implications of implementing a smart pressure management approach in regulating stations within a distribution network with a localized hydrogen injection. The research introduces a novel simulation-based optimization algorithm, incorporating a steady-state fluid-dynamic model with hydrogen tracking, used to optimize the pressure setpoints in the stations. The algorithm is applied to a two-pressure levels looped gas network with multiple gas supply nodes and a single hydrogen injection. The test case results reveal that utilizing dynamic pressure setpoints leads to a 22% increase in hydrogen penetration compared to standard operation. Therefore, this study highlights that smart pressure modulation in a gas network with hydrogen injection can unlock a latent decarbonization potential, while simultaneously adhering to safety limits.

Collision avoidance behaviours while young adults avoid a virtual pedestrian approaching on a 45° angle under attentionally demanding conditions

Individuals rely on visual information to determine when to adapt their behaviours (i.e., by changing path and/or speed) to avoid an approaching object or person. After initiating an avoidance behaviour, individuals may control the space (i.e., minimum clearance distance) between themselves and another person or object. The current study aimed to determine the action strategies of young adults while avoiding a virtual pedestrian approaching along a 45° angle in an attentionally demanding task. Twenty-one young adults (22.9 ± 1.9 yrs., 11 males) were immersed in a virtual environment and were instructed to walk along a 7.5 m path towards a goal located along the midline. Two virtual pedestrians (VP) positioned 2.83 m to the left and right of the midline approached participants on a 45° angle. To manipulate the point at which the participants and the VP would intersect during different trials, the VP approached at one of three speeds: 0.8×, 1.0×, or 1.2× each participants' average walking speed. Participants were instructed to walk to a goal without colliding with the VP while performing the attention task; reporting whether a shape changed above the VPs' heads. Results revealed that young adults did not modulate their timing of avoidance to the approach characteristics of the VP, as they consistently avoided the collision 1.67 s after the VP began moving. However, young adults seem to control how they avoid an oncoming collision by maintaining a consistent safety margin after an avoidance behaviour was initiated.

Research of biomimetic corrugation on the blade flutter suppression in large-scale wind turbine systems

Abstract Aiming at the blade flutter of large horizontal-axis wind turbines, a method by utilizing biomimetic corrugation to suppress blade flutter is first proposed. By extracting the dragonfly wing corrugation, the biomimetic corrugation airfoil is constructed, finding that mapping corrugation to the airfoil pressure side has better aerodynamic performance. The influence of corrugation type, amplitude λ, and intensity on airfoil flutter is analyzed using orthogonal experiment, which determines that the λ has the greatest influence on airfoil flutter. Based on the drag coefficient flutter index δ, the optimal airfoil flutter suppression effect is obtained when the type is III, λ=0.6, and intensity is denser (n=13). The effective corrugation layout area in the chord direction is determined to be the leading edge, and the δ of corrugation airfoil is reduced by 5.049%, compared to the original airfoil. The application of this corrugation to NREL 15 MW wind turbine 3D blades is studied, and the influence of corrugation layout length in the blade span direction on the suppressive effect is analyzed by fluid-structure interaction. It is found that when the layout length is 0.85R, the safety margin Sf reaches a maximum value of 0.3431 Hz, which is increased 2.940%. The results show that the biomimetic corrugated structure proposed in this paper can not only improve the aerodynamic performance by changing the local flow field on the surface of the blade, but also increase the structural stiffness of the blade itself, and achieve the effect of flutter suppression.

Isocycloseram: A new active ingredient for leaf-cutting ants control.

Leaf-cutting ants are the most important pests in several cropping systems in the Neotropics. Granulated baits containing active ingredients, considered hazardous by the Stockholm Convention, are the usual method to control these ants. Isocycloseram is a new insecticide molecule with high safety margin for mammals, but without registration for the ants in general. Thus, this study investigated the effectiveness of granulated baits with isocycloseram in leaf-cutting ants control under laboratory and field conditions. Initially, the mortality of Atta sexdens workers, fed with dehydrated citrus pulp paste containing different concentrations of isocycloseram was evaluated in the laboratory for 21 days, for toxicological classification. Subsequently, the loading, devolution, and incorporation of baits with different concentrations of isocycloseram and the mortality of A. sexdens colonies were evaluated in the laboratory. After that, the percentages of loading and devolution of baits, foraging activity, and colony mortality treated with 0.05, 0.1, 0.2, and 0.3% of isocycloseram were evaluated for the species A. sexdens, A. laevigata, and Acromyrmex lundii in field conditions. All concentrations of isocycloseram killed more than 15% of ants in 24 h and more than 90% in 21 days in the laboratory, being classified as a fast-acting and highly effective active ingredient. Baits with 0.001 to 0.03% of isocycloseram were highly loaded and exhibited low rate of devolution. The mortality of A. sexdens colony was higher at concentrations between 0.075 and 0.3%, in the laboratory. Baits containing isocycloseram at concentrations of 0.2 and 0.3% were highly loaded, presented low devolution rates, and were highly efficient in controlling A. sexdens, A. laevigata, and A. lundii in the field, at dosages of 6, 10, and 12 g/m² of nest. This is the first report of the use of isocycloseram against leaf-cutting ants, contributing to the development of efficient and toxicologically safer ant baits.

Lianas in tropical dry seasonal forests have a high hydraulic efficiency but not always a higher embolism resistance than lianas in rainforests.

Lianas have higher relative abundance and biomass in drier seasonal forests than rainforests, but whether this difference is associated with their hydraulic strategies is unclear. Here, we investigate whether lianas of seasonally dry forests are safer and more efficient in water transport than rainforest ones, explaining liana abundance patterns. We measured hydraulic traits on five pairs of congeneric lianas of the tribe Bignonieae in two contrasting forest sites: the wet 'Dense Ombrophilous Forest' in the Central Amazonia (~ 2 dry months) and the drier 'Semideciduous Seasonal Forest' in the inland Atlantic Forest (~6 dry months). We also gathered a broader database, including 197 trees and 58 liana species from different tropical forests, to compare hydraulic safety between habits and forest types. Bignonieae lianas from both forests had high and similar hydraulic efficiency and exhibited variability in resistance to embolism across forest types when phylogenetic relationships are taken into account. Three genera had higher hydraulic safety in the seasonal forest than in the rainforest, but species across both forests had similar positive hydraulic safety margin despite lower predawn water potential values of seasonal forest' lianas. We did not find the safety-efficiency trade-off. Merging our results with previously published data evidenced a high variability of resistance to embolism in both trees and lianas, independent of forest types. The high hydraulic efficiency of lianas detected here probably favors their rapid growth across tropical forests, but differences in hydraulic safety highlight that some species are highly vulnerable and may rely on other mechanisms to cope with drought. Future research on the lethal dehydration threshold and the connection between hydraulic resistance strategies and liana abundance could offer further insights into tropical forest dynamics under climatic threats.

Uncertainty Quantification of Engineering Parameters for a Nuclear Reactor Loaded with Dispersed Fuel Particles

Owing to their high intrinsic safety, dispersed fuel particles are an important fuel pattern for fourth-generation nuclear reactors. Due to the unique cladding layers and the random dispersion characteristics, dispersed fuel particles significantly differ from pressurized water reactors regarding operation-induced uncertainty. This study quantitatively analyzed overall uncertainty while considering a random distribution of dispersed fuel particles, material thickness, and fuel enrichment. The results demonstrated that, for all packing fractions, the uncertainty induced by the random dispersion of dispersed fuel particles was below 0.03%. For every packing fraction, the differences between the results obtained by the regular and the random distribution models increased, and then decreased, until reaching its maximum (1.297%) at 15%. Keff decreased as the radius of the UO2 kernel increased; Keff increased as the thickness of the cladding layer increased; the uncertainty of Keff was 1.003% when a random distribution of particles, material thickness, and fuel enrichment were taken into consideration; the uncertainty of the power distribution of reactor core assemblies was maximized (1.495%) at the edge of the reactor core. Quantitative analysis of uncertainty provides references for the optimization of design and safety margin analysis for reactors.

High temperature co-polyester thermoplastic elastomer nanocomposites for flexible self-regulating heating devices

Pyroresistive polymer composites are smart materials with great promise in numerous fields of electronic devices, including temperature and strain sensors, self-regulating heating, and over-current/over-temperature protective devices. However, the operational window of these materials is limited by the phase transition temperatures of the polymer matrix and the brittleness of the composites. Herein, a conductive polymer composite based on a co-polyester thermoplastic elastomer reinforced with graphene nanoplatelets (GNPs) was developed, which exhibits a positive temperature coefficient (PTC) switching temperature of 200 °C. This system shows a more gradual increase in resistivity with temperature and a less pronounced drop in resistivity past the critical transition temperature than other PTC composites. Moreover, Joule heating experiments revealed the ability to regulate at a predefined maximum temperature (within 150 – 200 °C), tuneable through parameters such as filler concentration, applied voltage and thermal boundary conditions, as also demonstrated by multiphysics simulations. Due to the more gradual PTC curve, this composite can produce steady state heating far below the PTC peak, unlike almost all other PTC materials: a unique advantage for self-regulating heating devices as the polymer is not in a melt state, reducing polymer degradation, filler mobility and increasing safety margin before onset of NTC behaviour.

Experimental study for inorganic and organic profiling of toy makeup products: Estimating the potential threat to child health.

Inorganic elements are added to toys as impurities to give desired stability, brightness, flexibility, and color; however, these elements may cause numerous health issues after acute or chronic exposure. In this study, the inorganic profile of 14 elements (Al, As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Se, Sb, Pb, and Zn) in 63 toy makeup products was identified by inductively coupled plasma-mass spectrometry after microwave acid digestion method. Additionally, organic allergen fragrance was investigated by gas chromatography-mass spectrometry. The systemic exposure dosage (SED), margin of safety (MoS), lifetime cancer risk (LCR), hazard quotient (HQ), and hazard indices were used to assess the safety evaluation. Then, 57 out of 63 samples (90.48%) exceeded the limits at least for one toxic element with descending order Ni > Cr > Co > Pb > Sb > Cd > As > Hg. The SED values were compared with tolerable daily intake values and remarkably differences were found for Al and Pb. The MoS values for 57.15% of samples exceeded the limit value for Al, As, Cd, Co, Hg, Mn, Sb, and Zn elements. The LCR values were observed at 100% (n = 63), 79.37% (n = 50), 85.71% (n = 54), 77.78% (n = 49), and 18.87% (n = 10) for Cr, Ni, As, Pb, and Cd, respectively. Also, the skin sensitization risks were obtained for Cr and Ni at 26.980% (n = 17) and 9.52% (n = 6), respectively. The HQ values for 80% of samples were found to be ≥ 1 at least for one parameter. The investigation of fragrance allergens in samples did not show any significant ingredients. As a result, toy makeup products marketed in local stores were found to be predominantly unsafe. Children should be protected from harmful chemicals by regular monitoring and strict measures.

A comparative analysis of 3D woven honeycomb-based aircrew helmet liners against Nomex and Aluminum alternatives

Abstract This study investigates the energy dissipation efficiency of an aircrew helmet liner developed using 3D woven honeycomb structural composites compared to different commercially available honeycomb liner materials such as Nomex, and Aluminium. In contrast to liners with discrete density differences, the use of a honeycomb-based liner reduces the concern about delamination, back face deformation and fracture propagation. The research involves comparing several parameters related to crashworthiness, such as specific energy absorption (SEA), crush force efficiency (CFE), and margin of safety, which are crucial for head protection and ensuring helmet injury tolerance. These parameters play a vital role in assessing the ability of different configurations of the honeycomb liner during impacts. Flatwise compression and dynamic impact tests were conducted to evaluate the helmet liner's performance while maintaining consistency in the helmet shell component. Finite element analysis (FEA) and 3D X-ray Tomography techniques were utilized to analyse the back face deformation (BFD) at high-velocity impact and the internal damage resulting from impacts on the helmet liners, respectively. The results revealed that the 3D woven honeycomb liner configuration performs optimally in terms of energy absorption by demonstrating sufficient and balanced competency across these three critical factors. Additionally, the simulation result revealed that the 3D woven honeycomb liner exhibits wave propagation. This phenomenon enhances its energy absorption capacity and reduces back-face deformation attributed to its crushing behaviour. This research offers valuable insights for improving the performance of aircrew helmet liners, with a particular focus on utilizing 3D woven honeycomb liners featuring 3D woven solid structure to maintain exceptional structural integrity.

A 3D spheroid model of quadruple cell co-culture with improved liver functions for hepatotoxicity prediction

Drug-induced liver injury (DILI) is one of the major concerns during drug development. Wide acceptance of the 3R principles and the innovation of in-vitro techniques have introduced various novel model options, among which the three-dimensional (3D) cell spheroid cultures have shown a promising prospect in DILI prediction. The present study developed a 3D quadruple cell co-culture liver spheroid model for DILI prediction via self-assembly. Induction by phorbol 12-myristate 13-acetate at the concentration of 15.42ng/mL for 48hours with a following 24-hour rest period was used for THP-1 cell differentiation, resulting in credible macrophagic phenotypes. HepG2 cells, PUMC-HUVEC-T1 cells, THP-1-originated macrophages, and human hepatic stellate cells were selected as the components, which exhibited adaptability in the designated spheroid culture conditions. Following establishment, the characterization demonstrated the competence of the model in long-term stability reflected by the maintenance of morphology, viability, cellular integration, and cell-cell junctions for at least six days, as well as the reliable liver-specific functions including superior albumin and urea secretion, improved drug metabolic enzyme expression and CYP3A4 activity, and the expression of MRP2, BSEP, and P-GP accompanied by the bile acid efflux transport function. In the comparative testing using 22 DILI-positive and 5 DILI-negative compounds among the novel 3D co-culture model, 3D HepG2 spheroids, and 2D HepG2 monolayers, the 3D culture method significantly enhanced the model sensitivity to compound cytotoxicity compared to the 2D form. The novel co-culture liver spheroid model exhibited higher overall predictive power with margin of safety as the classifying tool. In addition, the non-parenchymal cell components could amplify the toxicity of isoniazid in the 3D model, suggesting their potential mediating role in immune-mediated toxicity. The proof-of-concept experiments demonstrated the capability of the model in replicating drug-induced lipid dysregulation, bile acid efflux inhibition, and α-SMA upregulation, which are the key features of liver steatosis and phospholipidosis, cholestasis, and fibrosis, respectively. Overall, the novel 3D quadruple cell co-culture spheroid model is a reliable and readily available option for DILI prediction.

Thermal and hydraulic performance of volumetrically heated triply periodic minimal surface heaters

Advanced heat transfer surfaces, mainly Triply Periodic Minimal Surfaces (TPMSs) have great potential to increase heat transfer performance over traditional heat transfer surfaces due to their tortuous flow path and higher surface area-volume ratio. The emergence of additive manufacturing of nuclear fuel motivates experimental investigation of such advanced geometries in the context of a nuclear reactor core. This study employed a novel method to explore the performance of gyroid and diamond TPMS geometries. Volumetrically heated heaters were additively manufactured from conductive polymer filament, and airflow was used to simulate the convective heat transfer from the core within a nuclear reactor. The mass flow and volumetric generation rates were varied, local Nusselt number correlations were obtained using embedded thermocouples to measure the solid and fluid temperature, and friction factor correlations were developed using differential pressure measurements. The gyroid TPMS presented a friction factor 1.5 times higher than the diamond TPMS and 90 times that of the rod bundle. TPMS geometries showed Nusselt numbers 8–10 times higher than that of the rod bundle, also maintaining colder internal temperatures, which suggested that they could sustain 250–275 % higher power density than the rod bundle for a given centerline temperature. Hence, having the potential to greatly increase the safety margins and power output of a nuclear reactor core with similar volume.

Redundancy and reliability levels of post-tensioned and grouted concrete cross-section in case of tendon failure

Since the 1960 s and 1970 s, the prestressing steel used on post-tensioned concrete (PTC) bridges has been known to be susceptible to stress corrosion cracking (SCC). This can result in brittle rupture of the prestressing steel. Objective of this study is to evaluate the reliability levels achieved with assessment method developed for verifying crack behaviour before failure in cross-section of PTC bridges with cross-section loss of prestressing steel. Additionally, the study aims to investigate of tendon loss on crack before failure behaviour. This paper applies a reliability analysis for methodology based on robustness analysis on crack before failure behaviour in PTC with deteriorating prestressing steel. The analysis involves examining cross-sections with various design criteria. The effects of choices made in designing the PTC structure are analysed and noted to have a significant impact on the safety margin of the structure, while the deterioration of prestressing steel does not significantly decrease the ductility of the cross-section if certain conditions are met. The use of stricter serviceability limit-state (SLS) criteria used in past design results the greater safety margin for the structure in the event of tendon loss, which therefore makes it beneficial for structural redundancy in the ultimate limit state (ULS).

Automated online safety margin (GLIOVIS) for glioma surgery model

PurposeGlioblastoma is the most common type of primary brain malignancy and has a poor prognosis. The standard treatment strategy is based on maximal safe surgical resection followed by radiotherapy and chemotherapy. Surgical resection can be optimized by using 5-delta-aminolevulinic acid (5-ALA)–induced fluorescence, which is the current mainstay. Although 5-ALA–induced fluorescence has gained general acceptance, it is also limited by inter-observer variability and non-standardized fluorescence parameters. We present a new software for processing images analysis to better recognize the tumor infiltration margins using an intraoperative immediate safety map of 5-ALA–induced fluorescence. We tested this in a brain model using a commercial surgical exoscope.MethodsA dedicated software GLIOVIS (ACQuF-II, Advanced Colorimetry-based Quantification of Fluorescence) was designed for processing analysis of images taken on the Intraoperative Orbital Camera Olympus Orbeye (IOC) to determine the relative quantification of Protoporphyrin IX (5-ALA metabolite) fluorescence. The software allows to superpose the new fluorescence intensity map and the safety margins over the original images. The software was tested on gel-based brain models.ResultsTwo surrogate models were developed: PpIX agarose gel–integrated in gelatin-based brain model at different scales (1:25 and 1:1). The images taken with the IOC were then processed using GLIOVIS. The intensity map and safety margins could be obtained for all available models.ConclusionsGLIOVIS for 5-ALA–guided surgery image processing was validated on various gelatin-based brain models. Different levels of fluorescence could be qualitatively digitalized using this technique. These results need to be further confirmed and corroborated in vivo and validated clinically in order to define a new standard of care for glioblastoma resection.

A Method for the Rapid Propagation of Emergency Event Notifications in a Long Vehicle Convoy

Convoys composed of autonomous vehicles could improve the transportation and freight industries in several ways. One of the avenues of improvement is in fuel efficiency, where the vehicles maintain a close following distance to each other in order to reduce air resistance by way of the draft effect. While close following distances improve fuel efficiency, they also reduce both the margin of safety and the system’s tolerance to disturbances in relative position. The system’s tolerance to disturbances is known as string stability, where the error magnitude either grows or decays as it propagates rearward through the convoy. One of the major factors in a system’s string stability is its delay in sending state updates to other vehicles, the most pertinent being a hard braking maneuver. Both external sensors and vehicle-to-vehicle communication standards have relatively long delays between peer vehicle state changes and the information being actionable by the ego vehicle. The system presented here, called the Convoy Vehicular Ad Hoc Network (Convoy VANET), was designed to reliably propagate emergency event messages with low delay while maintaining reasonable channel efficiency. It accomplishes this using a combination of several techniques, notably relative position-based retransmission delays. Our results using Network Simulator 3 (ns3) show the system propagating messages down a 20-vehicle convoy in less than 100 ms even with more than a 35% message loss between vehicles that are not immediately adjacent. These simulation results show the potential for this kind of system in situations where emergency information must be disseminated quickly in low-reliability wireless environments.

Squamous Cell Carcinoma of the Lip: Clinical Presentation and Management Outcome

Background: Squamous cell carcinoma (SCC) is the second most common amongst skin cancers, following the basal cell carcinoma. SCC of the lip carries relatively better prognosis if detected early and treated adequately. Public awareness about the significance of early presentation would help to improve the outcome of management. Objective: The current study was conducted to determine the clinical presentation of lip SCC and management outcome with surgery as the primary treatment modality. Methods: This descriptive study was carried out at the National Institute of Rehabilitation Medicine, Islamabad over a period of seven years. All patients who presented with lip SCCs during the study period were prospectively included in the study. Non-consenting patients were excluded. The lesions were excised with 1-2-cm palpable macroscopic safety margins. Results: Out of 37 patients, there were 28 (75.67%) males and 9 (24.32%) females. The ages ranged between 47-79 years with a mean of 59.91±9.17 years. Lower lip was the most commonly affected site (n=30; 81.08%). The duration of the lesions at first presentation varied from 6-13 months with a mean of 7.32±1.79 months. Majority (n=31; 83.78%), of the patients had early stage (stage I and II disease) whereas 6(16.21%) patients had stage III disease. The margin clearance rate after initial excision of the lesions was 91.89%. Karapandzic flap was employed as reconstructive tool among 15(40.54%) patients. The 5-year overall survival rate was 62.16%. Conclusion: Lip SCCs were found more frequently among males aged over 50 years. Lower lip was the commonest seat of lip SCCs. Surgical excision with recommended safety margins was associated with tumor free margins in 91.89% cases. Karapandzic flap was the most useful reconstructive tool. The 5-year overall survival rate was 62.16%.

SUBSTANTIATION OF SOLUTIONS TO INCREASE THE DURABILITY OF THE INNER ROWS OF STEEL TEETH OF ROLLER CONE BITS DURING DRILLING OF BOULDER-PEBBLE ROCK FORMATIONS

The article deals with issues concerning the increase in the productivity of roller bits when drilling soft and soft-medium rocks with inclusions of boulder-pebble formations by justifying solutions to increase the relative safety margin of steel teeth expressed in an increase of the impact strength of the material for making cones in combination with an increase in the geometry of steel teeth. The efficiency of the rock-crushing tool and, as a result, the destruction of rock during the entire drilling cycle, directly depends on the resource and durability of the elements of the roller bit. When drilling the upper intervals of deposits in the East Siberian region, composed of soft and soft-medium rocks with inclusions of boulder-pebble deposits, there is a problem of premature wear of the drill bit. Both PDC bits are subject to catastrophic wear due to chips and fractures of PDC cutters, as well as roller bits. The use of first-class roller bits with steel teeth leads to advanced wear, expressed by the scrapping of the teeth of the inner rows. This leads to a «hanging» of the bit and a loss of mechanical penetration speed. Based on this, the work provides recommendations for increasing the durability of steel teeth for first-class roller cone bits.

Analisis Break Even Point dan Margin of Safety Sebagai Alat Perencanaan Laba Pada Usaha Tahu Sumber Mulya Kota Bengkulu

The purpose of this study was to determine the application of BEP and MOS as a profit planning tool in the Usaha Tahu Sumber Mulya in Bengkulu city. The data collection method used is unstructured interviews and documentation with qualitative and quantitative analysis methods using Break Even Point analysis. The results of the research, BEP the contribution ratio per unit of tofu was 41% with a business profit rate of 35.3% with a margin of safety of 86.1%. While the where the contribution ratio per unit of tofu was 49.2% with a business profit level of 44.1%, the level of security or margin of safety in 2022 was 89.8%. The use of BEP and Safety stock calculation provides an overview of the Usaha Tahu Sumber Multa in Bengkulu City, you can see the BEP for tofu production and safety stock in the warehouse, this is so that the production process continues and obtain the desired profit .

Numerical study of the effect of helical fuel rod geometry on single-phase flow and heat transfer characteristics

Helical fuel is a promising nuclear fuel proposed to improve the core power density and safety margin. In this study, the effect of helical fuel rod geometry on single-phase flow and heat transfer characteristics in helical fuel annuli has been investigated. The volumetric energy source is applied to the fuel pin, and coupled walls are used at the coolant-cladding and cladding-fuel interfaces. The numerical method with SST k-ω turbulence model has been validated with the results of bare annulus. The flow field, fuel central temperature, friction factor, and the circumferential distribution of swirl intensity, heat flux and wall temperature are obtained based on the numerical simulation. The increase in R2/R1 will result in broadening transverse flow region, reducing the gradient of surface heat flux and wall temperature, lowering the maximum wall temperature, but increasing the fuel central temperature and has no significant effect on the friction resistance. The decrease of helical pitch increases the swirl intensity and friction factor, but worsens the heat transfer at the blade roots.