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Miniaturised piezoelectric devices are emerging energy harvesting sources that are appropriate for various implantable and wearable applications. However, these piezoelectric devices exhibit considerable internal resistance due to their internal impedance, which leads to self-start and low-energy conversion failures. This paper describes a dual-stage boost converter circuit by facilitating self-powering features and boosting the low voltage harvested by the piezoelectric devices into dc. The proposed circuit comprises conversion stages of ac-dc and dc-dc in Stages I and II, respectively. In addition, the proposed circuit does not require employing the auxiliary circuits to generate the train pulses by triggering the bidirectional switches to envelop the current being stored in Stage II and kick-start the self-powered circuit for piezoelectric energy harvesting systems. Theoretical assumptions and control strategies were tested and verified with ideal and impedance input sources. The proposed circuit could convert a low voltage of 3 Vac into 19 Vdc. The maximum attained output power by the proposed circuit was 3.61 mW. The outcome depicted that the proposed circuit boosted the low voltage and outperformed the existing literature circuits in terms of output voltage and power.

Combining both processing techniques of horizontal-to-vertical spectral ratio (HVSR) and surface-to-borehole spectral ratio (SBR), using the KiK-net and K-NET database in Japan, could be used in the present study to establish relationships of VS and resonant frequency ( $$f$$ ) versus depth to bedrock half-space ( $$h$$ ) based on the site-dependent variability. Remarkable correlations of the average $${V}_{s}$$ of layers overlying the bedrock half-space ( $$\overline{{V }_{S}}$$ ) versus $$h$$ are inversely resembling those of the $$f$$ versus $$h$$ . The maximum $$\overline{{V }_{S}}$$ values are 1262 m/s, 933 m/s, 842 m/s, and 568 m/s through site class of B, C, D, and E, respectively. These values of $$\overline{{V }_{S}}$$ are decreasing gradually resembling the $${V}_{s30}$$ through site class of B, C, D, and E according to (NEHRP, Report FEMA 368, NEHRP, Washington, 2000). The $$f$$ versus $$h$$ regressions at KiK-net sites yield gradual decrease in the correlation coefficients (i.e., a and b) through site class of B, C, D, and E, particularly the resulted a and b from SBR technique. K-NET sites yield significant lower correlation coefficients, which could be attributed to the K-NET shallow depths ( $$h$$ ) and their corresponding limited ranges of ( $$f$$ ). Although such relationships are site-specific and highly dependent on each region’s geologic conditions, fair comparisons based on site information and site-dependent variability between previous relationships of $$f$$ versus $$h$$ in the literature and the present study relationships are showing remarkable similarities. This indicates significant importance of introducing the seismic site classification as a crucial controlling factor in establishing the previous and the present $${V}_{s}$$ and $$f$$ versus $$h$$ nonlinear regression relationships.

Cloud computing will continue to play a critical role due to its ability to deliver various types of on-demand information technology (IT) services according to customer needs. Unfortunately, cloud computing has faced many challenges. The task scheduling problem is considered one of the main challenges because the user has to pay for a resource. Therefore, a good mapping of users’ tasks on the available resources is required to reduce the total execution time of the users’ tasks (i.e., reduce makespan), execution cost, enhance load balancing, increase resource utilization, etc. Many heuristic algorithms have been existed to solve task scheduling problems. Although, the Heterogeneous Earliest Finish Time (HEFT) heuristic algorithm is considered one of the best task scheduling algorithms in a heterogeneous environment, it does not concern load balancing. In this paper, a modification has been introduced to the HEFT algorithm to satisfy load balancing. The modified algorithm is called Load Balancing HEFT (LB-HEFT). A comparative study has been done among the proposed LB-HEFT, the Enhancement Heterogeneous Earliest Finish Time (E-HEFT), and HEFT algorithms to evaluate the performance of the proposed LB-HEFT algorithm. According to the comparative results, it is found that the proposed LB-HEFT algorithm outperforms the existing E-HEFT and HEFT algorithms by improving load balancing by 43.49% and 72.59%, respectively in average, enhancing resource utilization by 2.28% and 5.61%, respectively in average, and reducing makespan by 7.55%, and 3.75% respectively in average.

The evaluation of groundwater presence by means of seismic wave velocities is of great concern for many hydrological related engineering applications. This work introduces a simple basic procedure to accurately and systematically identify groundwater levels using P‐wave and S‐wave velocities. This procedure is defined as a seismic reflectivity parameter and based on the seismic reflection coefficients of P‐wave and S‐wave at the unsaturated/saturated interfaces (i.e., groundwater level). The present procedure is applied to 1045 K‐NET sites in Japan. Observed velocity structures, accompanied by their bulk densities and detailed lithology, for the upper 20 m depth are obtained from the National Research Institute for Earth Science and Disaster Prevention, Japan. Calculations are carried out considering three distinct lithological conditions – gravel, sand and clay–silt sediments – in order to evaluate the ability of this approach (seismic reflectivity parameter) to detect the groundwater level and assess its practical limitations. The increase of the seismic reflectivity parameter value varies substantially with Poisson's ratio, resembling the relationship between VP/VS and Poisson's ratio in gravel, sand and clay–silt sediments. However, positive seismic reflectivity parameter values indicate groundwater presence, whereas negative seismic reflectivity parameter values indicate lithological variation. The seismic reflectivity parameter can also be used as a relative indicator for groundwater saturation levels. Fair comparisons are established between the seismic reflectivity parameter and the water seismic index technique. However, the seismic reflectivity parameter approach shows consistency with previous theoretical and experimental studies related to variations of VP and VS in saturated conditions, whereas the water seismic index shows inconsistency with these previous theoretical and experimental studies and an inability in determining saturation levels and detecting groundwater levels.

In this study, the inversion modeling method variability of S-wave velocity structure results by inverting/forward-modeling waveforms and HVSR curves is investigated. For this purpose, eight KiK-net seismic stations using 636 foreshocks, mainshock of the 2011 Tohoku earthquake, and 4983 aftershocks obtained from KiK-net are used. The most reliable and representative inverted S-wave velocity structures are based on close fitting of the theoretical to the observed data of waveforms and HVSR curves. The inverted S-wave velocity structures derived from the total stress analyses are showing high degrees of similarity and consistency using both EW and NS components and evidenced by the isotropic HVSRs directionality related to the linear and nonlinear site effects. Conversely, stiffness variations due to nonlinearity, inferred from inverted S-wave velocity structures derived from the diffuse field assumption, significantly correspond with stiffness variations evaluated from the observed fundamental resonance frequencies. The corresponding percent of reduction and recovery reflect low variability in S-wave velocities that result from inversion modeling based on diffuse field assumption. Qualitatively, the presence of the stiffness degradation process due to linear and nonlinear site responses could be obviously detected using both inversion modeling methods based on total stress analyses and diffuse field assumption. Quantitatively, the precision of the nonlinearity evaluation is questionable due to significant uncertainties in the inverted S-wave velocity structures inferred from both inversion modeling methods. These uncertainties are strongly dependent on the theory of each inversion modeling method. The use of complementary methods with more prior information is suggested to resolve the nonuniqueness of the inverted S-wave velocities and hence overconfidence in the precision of the nonlinearity evaluation.

In this study, a complete model for a miniature excitation-powered piezoelectric generator (PG), analysis modes of operation and control of a full-bridge joule thief (FBRJT) circuit to identify the optimal points were investigated. The proposed model revealed the PG’s power dependency on mechanical excitation, acceleration, and frequency and defined the load behaviour for power optimisation. The proposed circuit, namely FBRJT, was integrated with the conventional full-bridge rectifier (FBR) in Stage 1 for AC-DC conversion and with the joule thief circuit in Stage 2 for DC-DC conversion. This integration acted as a boost converter without utilising the duty cycles and additional switching components. The electrical nature of the input of FBRJT with a simple structure, sensor-less control and auxiliary circuits showed a consistent agreement with the investigated testing scenarios using both ideal and impedance power sources. Additionally, the performance of the proposed circuit was also verified against the published results of power electronics circuits. The developed versatile circuit and control system can be utilised for many applications, such as mobile battery charging and energy harvesting.

It is commonly accepted that the horizontal-to-vertical spectral ratio (HVSR) technique enables the detection of the fundamental resonance frequency ($$f_{\text{HVSR}}$$) of a given site. The utility of this $$f_{\text{HVSR}}$$ is analyzed using the nonlinear regression relationships between $$f_{\text{HVSR}}$$ and bedrock depth ($$h$$). The derived relationships are mostly site-specific, so that the present paper consists of two main parts. The first is a literature review for the available empirical relationships between $$f_{\text{HVSR}}$$ and $$h$$. The aim of this part is to highlight the practical limitations of these established relationships and to make fair comparisons. The second is to generate new relationships, taking advantage of the very wide range of available lithological, geophysical, and geotechnical borehole drilling data of the 697 KiK-NET seismic stations in Japan. For this purpose, HVSR are calculated using 10,000 weak earthquakes or linear events recorded at KiK-NET stations to determine the $$f_{\text{HVSR}}$$ and correlate it with the corresponding $$h$$. The overlying layers/bedrock interface falling within sedimentary, igneous, or metamorphic layers significantly affect the derived frequency–depth relationships. In addition, these relationships are strongly reproduced by the $$V_{\text{p}} /V_{\text{s}}$$ ratio of the bedrock in the range of 1.6–2.2. Interestingly, it is found that $$f_{\text{HVSR}}$$ less than 1 Hz corresponding to $$h$$ more than 100 m leads the trend of the overall frequency–depth relationship.

Background Cerebral edema and increased intracranial pressure are of the major consequences of traumatic brain injury that affects the outcome. The aim of this study is to assess the efficacy of dexmedetomidine as an adjunct to conventional sedative therapy (propofol) compared to conventional sedative therapy alone in patients with traumatic brain injury, as regards its effects on hemodynamics and intracranial pressure. Methods This prospective randomized controlled clinical trial with 60 agitated and restless traumatic brain-injured patients was performed between May 2013 and May 2017. Patients who required mechanical ventilation, Glasgow coma scale (GCS)

The main problem associated with using composite sandwich panels with foam core is their ability to withstand shear load. The aim of the present work is to extend the knowledge of mechanical properties both on constituent components and on the whole sandwich structures, focusing on the effects induced by inserting semi-circular shear keys between the skin and the foam core. The sandwich panel under investigation is composed of glass fibre reinforced polymer (GFRP) skin with polyvinylchloride (PVC) and polyurethane (PU) foam core, while the shear keys are made of chopped strand (CS) glass fibre impregnated with epoxy resin. The material properties of the skin, keys and foam core materials were investigated through a series of quasi-static tests. The mechanical properties of each component were used as input data in order to implement the finite element (FE) analysis using ABAQUS software. Parametric investigation using the FE analysis to select the most suitable pitch (space between shear keys along the panel) of the shear keys taking into consideration the materials and geometrical nonlinearities as well as the complex interaction between all the mating surfaces was performed. Five different pitches have been investigated namely 15, 25, 35, 45 and 55 mm. The results showed that the model with 45 mm pitch represents the most sustainable model among the others. The FE results were verified with the measured ones extracted from the out-of-plane shear test.

Prognosis of colorectal carcinoma depends on many factors, such as age and sex of patient; location; multiplicity; local extent and size of tumor, bowel obstruction, or perforation; as well as tumor microscopic type and grade; vascular and perineural invasion; and nodal and distant metastasis. The matrix metalloproteinases (MMPs) are a family of proteolytic enzymes strongly implicated in tumor invasion and metastasis, hence in tumor prognosis. The purpose of this study was to assess the role of MMP-2 and MMP-9 expression in colorectal tumorigenesis, invasion, and metastasis, hence their prognostic values.Immunohistochemical analysis of MMP-2 and MMP-9 in colorectal cancer cells, an immunohistochemical score based on the intensity of immunoreactivity and proportion of immunoreactive cells that established for each MMP, and correlation of this expression with the established prognostic factors.MMP-2 was expressed in 81.8% (strong expression in 40%) of cases, and MMP-9 was expressed in 72% (strong expression in 35%) of cases.MMP-2 and MMP-9 are widely expressed in colorectal carcinoma, suggesting significant diagnostic and prognostic values in these tumors. Increased levels of MMP-2 and MMP-9 protein expression in colorectal carcinoma tissues as compared to normal tissues suggest their association with colorectal tumor invasion and metastasis and that they could be targets for intervention and therapy in colorectal carcinoma.

Gallstones are more common in patients with liver cirrhosis than in healthy individuals. Higher morbidity and mortality were reported in cirrhotic patients with either laparoscopic or open cholecystectomy. The aim of this study was to compare laparoscopic and open cholecystectomy in cirrhotic patients with symptomatic cholelithiasis in a prospective, randomized manner.Thirty patients with symptomatic cholelithiasis associated with Child-Pugh class A or B liver cirrhosis were prospectively and randomly grouped equally to either laparoscopic or open cholecystectomy. The two groups were compared regarding operative time, morbidity, mortality, postoperative liver function, and hospital stay.The two groups were comparable regarding demographic data, preoperative and postoperative Child-Pugh scoring, mean operative time (57.3 minutes for laparoscopic and 48.5 for open), and complications (33.3% for each). Hospital stay was shorter for the laparoscopic group. One conversion (6.7%) to open surgery was reported. No periopertive mortality occurred in either group.For Child-Pugh class A and B cirrhotics, laparoscopic cholecystectomy is comparable to the open approach regarding operative time, morbidity, mortality, and effect on liver function, but with shorter hospital stay. Considering the other well-documented advantages of the laparoscopic approach, namely, less pain, earlier mobilization and feeding, and better cosmoses, laparoscopic cholecystectomy would be the first choice in cirrhotic patients.