Weight and configuration optimization of the launcher pod using finite element analysis

This paper deals with the stress analysis of the launcher pod based on optimization of its configuration and weight without compromising its strength and stiffness. The launcher pod assembly is a complex fabricated structure, which is subjected to a variety of dynamic loads during firing of rockets. A series of finite element simulations reveal the critical location of the pod for different loading conditions based on the stress magnitude, which helps to optimize its weight and configuration of the launcher pod. It has been observed that the optimized weight of the given launcher pod after modification of materials and configuration, with the provided materials, loading, and boundary conditions, is reduced by 36.27% (without launcher tubes and rockets) against the initial weight of the launcher pod.

Ferrocement as a Retrofitting Material for Beam Column Joint

Structure safety is of utmost importance in modern days. Now- a- days ferrocement is gaining popularity as a retrofitting material due to ease of its application and availability. The most critical location of failure in any structure is beam column joint. The aim of this paper is to analyse the effect of retrofitting on beam column joint using ferrocement as a retrofitting material. Square wire mesh and triangular wire mesh was used for retrofitting beam column joint. Beam column joint is designed using ductile detailing code IS 13930:2016. Axial and reverse cyclic displacement load is applied on the specimen. Further unstrengthen and strengthened specimen were analysed using ANSYS software. A comparative study was done and it was concluded that after retrofitting, the specimen shows considerable decrease in total deformation. It shows that retrofitted beam column joint was more stable than the unstrengthened beam column joint. So, to increase the serviceability of any structure it is recommended to retrofit the structure. Keywords: BCJ, ferrocement, wire mesh, retrofitting

Mathematical Model of a Tonal Rail Chain without Insulating Joints with Current Receiver in Shunt Mode

One of the drawbacks of the currently used tonal rail chains without insulating joints is that when the train approaches the controlled section, the train begins to shunt this section at some distance before entry on him. In connection with the traffic light moves on this distance. But being that this distance depends on many variables, it constantly changes these variables. For eliminate this drawback, instead of the traditional potential receiver it is proposed to use electric current track receiver, which has a clear boundary fixation entry of train on the controlled section. By now developed and used methods for determining the main analytical expressions for analysis and synthesis tonal rail circuits with potential receivers in various operating modes, and the theoretical issues of tonal rail chains with current receivers were practically not considered, in this connection, the article considers the development of mathematical models for determining the absolute shunt sensitivity of tonal rail chains without isolating joints with current receivers and methods for calculating determination of the critical location of the minimum shunt sensitivity. The obtained expressions differ significantly from the known equations of absolute shunt sensitivity and the critical location of the minimum value of the shunt sensitivity and will allow to spend analyzing, synthesis and design of tonal rail chains without isolating joints with current receivers, that will allow to increase the safety of train traffic.

Management of The Posterior Cerebral Fossa Ependymomas

Background Posterior fossa brain ependymomas are one of the most devastating forms of human illnesses which are more common in children. Brainstem compression, herniation and death are the risks with tumours in this critical location. Patients and Methods: A retrospective study including 50 patients with posterior fossa ependymoma were performed at the Neurosurgery Department in Ait IDDIR University Hospital between the period of January 2005 and December 2015 . In each case, diagnosis was made clinically and confirmed radiologically and histo-pathologically.. All patients received the adjuvant treatment Results Out of 50 patients, 30 (60%) patients were males and 20 (40%) were females. The mean age was 24 years (ranged 5 months –47 years) ; we identified 29 (58%) children and 21 (42%) adults,. Ventriculo-peritoneal shunts were placed in all our patients, the total tumor excision was done to 35% and the partial tumor excision was done to 65% patients. The most common complications were as follows: Shunt malfunction : 4% , operative cavity hematoma 6%, CSF fistula 4%, deterioration of Cerebellar syndrome 6%, Cerebellar Mutism 2%, Mixed nerves palsy 4% and early post operative deaths 10%. Tumor architecture was classified as classic (Grade II) in 35 (70%) cases and anaplastic (Grade III) in 13(26%) cases. Adjuvant treatment regimens following resection included radiation therapy only (72%) for 36 patients including children above and adults and chemotherapy only (36%) for 9 children below 4 years and 9 recurrent tumors. During follow-up period, recurrence occurred in 27% 11patients out of 41patients .Five patients died (10%). Conclusion The surgical treatment of posterior fossa tumours still represents a challenge for neurosurgeons, Radical surgery with preservation of vital structures is the treatment of choice in patients with Posterior Cerebral Fossa ependymomas.Our experience shows the accepted results, complications and surgical outcome in relation to previous clinical studies.

Analogue representation of a spatial memory by ramp-like neural activity in retrohippocampal cortex

When solving navigational problems, remembering that a critical location is approaching can enable appropriate behavioural choices without waiting for sensory signals. Whereas multiple types of neuron in the hippocampus and retrohippocampal cortex represent locations using codes based on discrete spatial firing fields, analogue neural representations may be advantageous for efficiently recalling proximity to locations of behavioral importance. Here, we identify retrohippocampal neurons that use analogue ramp-like changes in firing rate to represent location as mice navigate a virtual environment in which they have learned the location of a reward. Ramp-like firing patterns had positive or negative slopes and could switch polarity or reset their rate at the reward location. These transitions were maintained when location cues were removed, indicating that path integration is sufficient to drive recall of the track structure expressed through ramp-like codes. We suggest that analogue ramp-like representations encode learned models for goal-directed navigation.

Investigation on the Stability of Fissured Slopes Reinforced with Anchor Cables under Seismic Action

Based on the upper bound theorem of limit analysis (UBLA) combined with the pseudostatic methods, this paper elaborates on a calculated procedure for evaluating fissured slope stability under seismic conditions reinforced with prestressed anchor cables. An existing simple slope case is presented as a case study in this work. The comparison is given to verify that the solution derived from this study is correct and feasible. By means of a numerical optimization procedure, the critical location of the crack is determined from the best upper bound solutions. The results demonstrate a significant influence of the depth of crack and seismic acceleration coefficient on the critical location distribution of the cracks. Meanwhile, the axial force of anchor cables is investigated via parametric studies. It is shown that the variation of the crack depth has little effect on the axial force of anchor cables. Moreover, this paper also illustrates the variation in the axial force of anchor cables under the impact of five marked factors (crack depth, anchor arrangement, anchor inclination angle, slope angle, and seismic conditions). Finally, the required critical length of the free section of anchor cables is determined to ensure the stability of fissured slopes subjected to seismic action.

Comparative Analysis of Radiofrequency Ablation and Microwave Ablation for Critically Located Hepatocellular Carcinomas Smaller than 5 cm

Purpose To compare the safety and efficacy of radiofrequency ablation (RFA) versus microwave ablation (MWA) for hepatocellular carcinomas (HCC) smaller than 5 cm in critical locations. Methods Single-center retrospective study of all patients who underwent RFA/MWA for HCC from July 2015 to Dec 2019. Critical location includes exophytic tumors, tumors ≤ 5 mm from the diaphragm, heart, gallbladder, kidney, gastrointestinal tract, and ≤ 10 mm from large vessels with caliber of ≥ 3 mm. Treatment effectiveness, local tumor progression, and complication rates were evaluated. Results Out of 119 patients with 147 HCC nodules in critical location, 65 (M:F = 49:16; mean age–61.7) were included in RFA group and 54 (M:F =43:11; mean age–60.5) in MWA group. Mean follow-up period was 16.5 and 14.8 months, respectively. At first follow-up imaging, 66/78 tumors in RFA group and 57/69 tumors in MWA group showed complete ablation with primary treatment effectiveness rates of 84.6% and 82.6%, respectively (p = 0.741). Local tumor progression (LTP) rate was 21.8% (17/78) and 20.3% (14/69), respectively (p = 0.826). Median time to LTP was 12 and 13.5 months, respectively. Fourteen tumors in RFA group and 12 in MWA group underwent reablation with a secondary treatment effectiveness rates of 78.6% (14/17) and 83.3% (12/14), respectively (p = 0.757). Mean LTP-free survival was 37.2 and 28.1 months, respectively. The total complication rate was 36.9% and 31.5%, respectively (p = 0.535) with no major complications in both the groups. Conclusion Our data suggest that both MWA and RFA are equally safe and effective for treating HCCs < 5 cm in critical locations.

Evaluation, repair & rehabilitation of 2 flyovers using advance assessment methods – a case study

<p>After the collapse of Majherhat Bridge on September 4, 2018 at Kolkata (India), an expert committee was appointed by the state government to ‘examine’ all the old flyovers in the city. A large number of such flyovers identified by this committee, which needed urgent repairs. Two of these flyovers were investigated by the authors as a part of consultancy services provided to the owner client. Both these grade separators were in distress and needed urgent attention. But carrying out condition assessment on these bridges and carrying out any repair posed a big challenge to the Consultants and Clients due to number of factors, including lack of records of the bridges, volume of traffic and critical location of these infrastructures. This paper highlights the broad details of advance assessment techniques adopted for structural condition of these flyovers. The details of proposed repair and rehabilitation techniques adopted are also discussed.</p>