Bi-directional Cyclic Behaviour and Liquefaction Analysis of a silica-carbonate sand

The cyclic behavior and liquefaction behavior of reconstituted samples of a local silica-carbonate sand are examined by performing monotonic and cyclic simple shear tests in addition to bender element shear wave velocity measurements. Shear wave velocity was found to vary with effective overburden stresses by an average power of 0.25. Maximum shear modulus (Gmax) was also computed from the shear wave velocity measurements and a correlation was developed between Gmax, effective stress and void ratio. Small strain and cyclic strain dependent shear modulus of the soil were determined, and shear modulus reduction curves were obtained. The results show a slower degrading stiffness and damping ratio, compared to an average proposed for sands. A critical state line of the samples was developed by performing drained and constant-volume monotonic simple shear tests. Cyclic resistance, shear wave velocity and rigidity factors of the sand samples were evaluated with the critical state approach. Circular, elliptical (oval) and figure-8 bi-directional cyclic load patterns were applied, in addition to mono-directional shearing modes and cyclic response of loose (25% relative density), medium dense (45% relative density), and dense samples (65% relative density) were investigated. Wide ranges of the generated excess pore water pressure ratio (ru) were observed. Changing patterns of ru values were assessed based on the cyclic shear strength of multiple tests and number of cycles prior to liquefaction. Also, the test results showed up to 35% reduction in cyclic resistance of bi-directionally loaded samples relative to mono-directionally loaded ones, which is the least for an elliptical cyclic pattern and the most for a circular cyclic pattern. Bi-directional cyclic results are found to be dependent on the loading pattern, and confining stress, and under-estimated by currently proposed coefficients. Critical state analysis was used for evaluating the cyclic resistance of the samples under different cyclic load patterns and the results were correlated to shear wave velocity parameter of samples. In addition, liquefaction susceptibility of the samples was evaluated and compared to previous research studies based on bi-directional cyclic tests, which suggests that current procedures may overestimate cyclic resistance of the soils based on shear wave velocity measurements. Moreover, the behaviour of samples was investigated for multiple liquefaction occurrences by applying a second cyclic load to specimens after the occurrence of a first liquefaction. Densification of samples due to repeated cyclic load application was observed and evaluated. The cyclic resistan ce of samples was assessed in consecutive liquefaction events. Results show a general decreasing resistance for loose samples which is more significant for mono-directional load patterns rather than bi-directional patterns. The resistance changes of medium dense samples from first to a second liquefaction is negligible and almost consistent for all load patterns. For dense samples, there is a distinction in the behaviour of samples under mono-directional shear patterns and bi-directional patterns. Although the majority of samples get more resistant to a second liquefaction under mono-directional loads, more complicated behavior was observed for dense samples as well as medium dense samples in large consolidation stresses under bi-directional cyclic loads. It was found that when applied shear loads get larger, the resistance of the samples decreases (becomes more liquefiable); inversely, when shear loads get smaller, the behavior changes to an increasing resistance and less liquefiable response. Pore water pressure generation of the samples was also studied. The results showed the quicker development of pore water pressures during first cyclic loading compared to the second cyclic loading stage for almost entire cyclic load patterns regardless of soil initial relative density. However, pore water pressure generation was found to be dependant on initial consolidation stresses

Confusing Hypoxia in a 21-Year-Old Intubated Multiple Trauma Patient

A 21-year-old man was brought to the emergency department due to multiple trauma (MT) caused by a motor car accident (MCA). On arrival, the patient was intubated by prehospital emergency medical services (EMS) and had a Glasgow coma scale (GCS) score of 6 on 10 (Due to intubation, verbal score was omitted). Physical examination revealed blood pressure of 150/70 mmHg, oxygen saturation (O2sat) of 60%, and pulse rate of 110/min. Examination of the tracheal tube site revealed incorrect esophageal placement. The patient was intubated again and his O2sat improved and reached approximately 96%. His pupils were reactive and of the same size. The Doll’s eye was normal, and plantar reflex was neuter in both sides. Neither expanding hematoma nor emphysema was observed in his neck. Laceration was noted on his left ear, but otorrhagia and tympanic perforation were not found. The lung sounds were normal in both sides. Extended focused abdominal sonography for trauma (e-FAST) examination revealed the absence of free fluid in the abdomen and pericardial space. No deformity of limbs was noted and the distal pulses were palpable. The patient’s O2sat decreased during his admission to the emergency department, and further examination indicated obvious decreased sound in his right lung that could not be reversed by needle thoracostomy. On reviewing his previous chest computed tomography, an obvious questionable pathology was detected in his right side Figure 1.What is your diagnosis

Operand Folding Hardware Multipliers

This paper describes a new accumulate-and-add multiplication algorithm. The method partitions one of the operands and re-combines the results of computations done with each of the partitions. The resulting design turns-out to be both compact and fast. When the operands' bit-length $m$ is 1024, the new algorithm requires only $0.194m+56$ additions (on average), this is about half the number of additions required by the classical accumulate-and-add multiplication algorithm ($\frac{m}2$)

Characterization of a Carbonate Sand based on Shear Wave Velocity Measurement

Numerous studies have been carried out on the dynamic behavior of sands. However, few studies have investigated the dynamic characteristics of carbonate sands. This paper presents series of laboratory simple shear tests on specimens of a local carbonate sand from London (ON). Besides monotonic and cyclic shearing, the dynamic behavior of the sand is also characterized by measuring the velocity of shear waves travelling through the specimens. Drained and undrained shearing behavior of specimens with a wide range of relative density and consolidation stresses are tested. Shear wave velocity is found to vary with effective overburden stresses by an average power of 0.25. Maximum shear modulus (Gmax) is also computed from the shear wave velocity measurements and a correlation is developed between Gmax, effective stress, and void ratio for a carbonate sand. The critical state line of the carbonate sand established from the simple shear tests is used for determining the state parameter of each specimen and this is related to the shear wave velocity measured in the same specimen. Such a relationship can be employed for measuring the in-situ state of this carbonate sand. Cyclic resistances of the sand specimens are determined from cyclic shear tests. Combined with shear wave velocity data, these are compared with current liquefaction triggering curves

Study the factors affecting the choice of higher education nonprofit institutions from candidate’s view (Case study: Preuniversity students in Qaemshahr)

This study was conducted to investigate the factors affecting the choice of higher education nonprofit institutions by pre-university students in Qaemshahr.From the population of the study 3176 people is randomly selected and a questionnaire was used to collect data that its reliability is 91/0 and its validity was approved by using the same external research and opinions of experts and university professors, finally, data from 320 students were analyzed by using SPSS software. Toanalyze the data t-test and Friedman test was used. The results show that among the studied variables,  including economic factors, factors related to the university, personal factors and social factors, economic factors are most important to students and social factors are the least important.Key words: economic factors, factors related to the university, personal factors, social  factors, higher education non-profit institution

Evaluating the Relationship between Operating Speed and Collision Frequency of Rural Multilane Highways Based on Geometric and Roadside Features

Speed is one of the main functional factors that affect road safety in terms of both collision occurrence and collision severity. Previous studies have shown that several roadside and geometric features affect road safety and operating speed. This paper aims to evaluate the effects of roadside and geometric features on operating speed and collision frequency, simultaneously. For this purpose, the operating speed data of 103 segments along with their accident data and roadside and geometric characteristics were collected. Structural equation modelling (SEM) with latent variables was employed to model operating speed and collision frequency, simultaneously. Two latent variables including “geometric effect” and “roadside effect” were defined in SEM. The first latent variable is the combination of the natural logarithm of the segment length, longitudinal slope, the presence of a 2-meter paved shoulder, and curvature of the segment. The indicators of the second latent variable are the number of accesses and the presence of residential land use. The results show that the latent variable “roadside effect” increases collision frequency by a standard regression weight of 3.455; however, it reduces operating speed by a standard regression weight of –0.385. Also, the latent variable “geometric effect” causes an opposite effect on collision frequency and operating speed by the standard regression weight of –5.313 and 0.730, respectively. Besides, lower operating speed causes a reduction in the collision frequency by the standard regression weight of 7.734. The results of this study can be useful for designers and road safety agencies to improve road safety

Upper Gastrointestinal Bleeding as Delayed Presentation of Traumatic Diaphragmatic Hernia: a Case Report

Introduction: Traumatic diaphragmatic hernia (TDH) is one of the critical complications resulting from penetrating chest trauma. The rate of undiagnosed TDH equivocates 12-60%. The significant part of complications happens 1-4 years after the primary damage. Here, we report a case of delayed TDH presented with upper gastrointestinal bleeding (GIB) as an excuse to discuss this issue. Case presentation: The patient was a 35-year-old man, admitted with objection of abdominal pain. A nasogastric tube was inserted and fixed that resulted in drainage of about 500cc dark blood. He was candidate for emergent endoscopy due to upper GIB. During resuscitation measures, he suddenly developed respiratory distress that could not be justified by upper GIB alone. Therefore, bedside sonography discovered some soft tissue apart from lung tissue in the left hemithorax. After performing diagnostic measures, with diagnosis of diaphragmatic herniation and strangulation he underwent emergent surgery. Conclusion: Small diaphragmatic lesions, which usually result from stab wounds, may develop into larger injuries if left untreated and they might lead to a diaphragmatic hernia with a potential risk of early or late complications and mortality. One of the rare complications is GIB, which should be considered in a patient with past history of trauma and presentation of GIB

Effectiveness of the Concurrent Intravenous Injection of Dexamethasone and Metoclopramide for Pain Management in Patients with Primary Headaches Presenting to Emergency Department

Introduction: Headache is a common reason for visiting emergency departments, and pain control is a major therapeutic goal in patients with headaches. Objective: The present study was conducted to examine the effectiveness of the concurrent intravenous administration of dexamethasone and metoclopramide in pain control in patients presenting to emergency departments with complaints of primary headache. Methods: This quasi-experimental study examined patients with moderate to severe headache attacks presenting to emergency departments. An 8-mg dose of dexamethasone and a 10-mg dose of metoclopramide were intravenously administered to the patients. The degree of headache was measured and recorded using the Numeric Rating Scale (NRS) upon admission and one hour and two hours after the injection. Results: A total of 51 patients with a mean age of 38.3±10.5 years participated in the study. The patients’ mean pain score was 8.4±1.3 upon admission and reduced to 6.2±2.3 one hour after the administration of the medication and to 3.1±2.9 two hours after the administration, suggesting significant reductions on both occasions (P<0.05). The therapeutic success was 39.2% one hour after the administration of the medication and 84.3% two hours after the administration. Conclusion: Based on these findings, the concurrent administration of dexamethasone and metoclopramide appears to affect the control of headache intensity in patients with primary headaches presenting to emergency departments

Supramolecular Structure and Mechanical Properties of Wet-Spun Polyacrylonitrile/Carbon Nanotube Composite Fibers Influenced by Stretching Forces

The effect of different elongation conditions on the crystalline structure and physical and mechanical properties of polyacrylonitrile/carbon nanotube (PAN/CNT) microfibers during the wet spinning process was studied. It turns out that the response of polymer chains in PAN/CNT and in PAN fibers to the stretching forces from jet stretching and steam drawing is different. The X-ray diffraction (XRD) results showed that the crystalline domain size in steam-drawn PAN/CNT fibers is 1.5 times larger than in PAN fibers. CNTs alter the optimum stretching conditions, as they improve the crystalline structure of the PAN/CNT fibers at lower steam drawing ratios than PAN fibers, through nucleation of crystals on their surface. Synchrotron-radiation XRD studies revealed that the presence of CNTs improves the crystal orientation of PAN/CNT fibers significantly. In addition, steam drawing is more effective in improving the crystal orientation than jet stretching. The mechanical properties of PAN/CNT fibers have also been affected by steam drawing more than jet stretching. Multiwalled CNTs have the biggest impact on Young's modulus. The Young's modulus of PAN/CNT fibers could increase up to 19% higher than PAN fibers at specific stretching conditions, i.e., steam drawing ratio of 2.5. Better orientation of polymers and crystals in the fiber direction is the reason for the enhancement of Young's modulus. To our knowledge, the differences between the response of PAN/CNT and PAN fibers to stretching forces inside coagulation bath and after fiber coagulation as well as the difference in evolution of crystalline structure at different stretching stages has not been reported elsewhere

Differential Analysis of Round-Reduced AES Faulty Ciphertexts

International audienceThis paper describes new Round Reduction analysis attacks on an Advanced Encryption Standard (AES) implemen- tation by laser fault injection. The previous round reduction attacks require both of spatial and temporal accuracies in order to execute only one, two or nine rounds. We present new attacks by more flexible fault injection conditions. Our experiments are carried out on an 8-bit microcontroller which embeds a software AES with pre-calculated round keys. Faults are injected either into the round counter itself or into the reference of its total round number. The attacks may result to the use of a faulty round key at the last one or two executed rounds. The cryptanalysis of the obtained round-reduced faulty ciphertexts resorts to the differentiation techniques used by Differential Fault Analysis