Load Standard Deviation Research Articles

An Optimum User Association Algorithm in Heterogeneous 5G Networks Using Standard Deviation of the Load

Fifth-generation (5G) wireless networks and beyond will be heterogeneous in nature, with a mixture of macro and micro radio cells. In this scenario where high power macro base stations (MBS) coexist with low power micro base stations (mBS), it is challenging to ensure optimal usage of radio resources to serve users with a multitude of quality of service (QoS) requirements. Typical signal to interference and noise ratio (SINR)-based user allocation protocols unfairly assign more users to the high power MBS, starving mBS. There have been many attempts in the literature to forcefully assign users to mBS with limited success. In this paper, we take a different approach using second order statistics of user data, which is a better indicator of traffic fluctuations. We propose a new algorithm for user association to the appropriate base station (BS) by utilizing the standard deviation of the overall network load. This is done through an exhaustive search of the best user equipment (UE)–BS combinations that provide a global minimum to the standard deviation. This would correspond to the optimum number of UEs assigned to every BS, either macro or micro. We have also derived new expressions for coverage probability and network energy efficiency for analytical performance evaluation. Simulation results prove the validity of our proposed methods to balance the network load, improve data rate, average energy efficiency, and coverage probability with superior performance compared with other algorithms.

IPSO Task Scheduling Algorithm for Large Scale Data in Cloud Computing Environment

Task scheduling is one of the essential techniques in the cloud computing environment. It is required for allocating tasks to the proper resources and optimizing the overall system performance. Particle swarm optimization (PSO) algorithm is one of the most popular scheduling algorithms, which is used to maximize resource utilization. However, the performance of the PSO scheduling algorithm decreases when the number of tasks is significant. In this paper, the improved PSO (IPSO) algorithm is proposed to provide the optimal allocation for a large number of tasks. This is achieved by splitting the submitted tasks into batches in a dynamic way. The resources utilization state is considered in each creation of batches. After getting a sub-optimal solution for each batch, the algorithm appends all the sub-optimal solutions for batches into a final allocation map. Finally, IPSO tries to balance the loads over the final allocation map. The proposed algorithm is compared with different scheduling algorithms, namely, honey bee, ant colony, and round-robin algorithms. The results of experiments show the efficiency of the proposed algorithm in terms of makespan, standard deviation of load, and degree of imbalance.

다양한 정규화 방법에 따른 평일 단기 전력수요예측 정확도 분석

The short-term load forecasting is necessary for stable and smooth power system operation. The accuracy of short-term load forecasting for weekdays according to various normalization methods is analyzed. The normalization methods to be analyzed are maximum and minimum normalization, maximum normalization, and Z-Score normalization. And the model used for 24-hours load pattern prediction is the exponential smoothing technique. In order to return the normalized 24-hour load value to the load value, the predicted maximum load, minimum load, average load and standard deviation of load are estimated using exponential smoothing. In the recent three-year case studies, the accuracy of the short-term load forecasting applying maximum normalization, maximum and minimum normalization and Z-Score to the exponential smoothing technique is analyzed based on the mean absolute percentage error(MAPE). The test results show that the maximum and minimum normalization method is better than the others.

Efficient Fault Tolerant Algorithms for Internet Distributed Systems

In the current era, Internet is the fastest growing technology. It is a global network of distributed systems that interconnects with each other to share various resources and computation. The complexity of the distributed systems is rapidly increasing, which leads to an increased susceptibility of failure to the participating computers such as clients and servers and their interconnections. Therefore, the main challenge is to address such failures and develop efficient algorithms to tolerate such failures. In this paper, four fault tolerant algorithms, namely server-based fault tolerant (SFT), client-based fault tolerant (CFT), client-server fault tolerant (CSFT) and connection fault tolerant (CoFT) are proposed to deal with the above challenge. The proposed algorithms are evaluated in terms of number of failures (NOF), load factor (LF) and load standard deviation (LSD) and compared with an existing algorithm. The comparison results show the superior performance of the proposed algorithms.

Influence of abutment design on retention of metal copings cemented to implants

Objective The study evaluated the influence of abutment design on the retention of implant-cemented metal copings.Material and methods Two abutments of the same system with the same indications, height and the total occlusal convergence, but of different designs were evaluated. Ten RN synOcta abutments (Straumann, Waltham, MA) and ten RN titanium solid abutments (Straumann, Waltham, MA) were tightened to 35 Ncm on 20 implant analogs previously placed in resin blocks. Twenty plastic burnout copings were waxed, included, cast and machined by a single operator. Coping was inspected for surface irregularities using a stereomicroscope at 10x magnification, and then, they were cemented (Temp Bond NE, Kerr, Romulus, MI) with 5 kg load for 10 min. The samples were stored for 24 h in room temperature and 100% humidity and then subjected to pull-out test at a crosshead speed of 0.5 mm/min. The load required to dislodge each coping was recorded (kgf) and and mean values for each group statistically calculated. Means and standard deviations of loads at failure were analyzed using Student’s t-test.Results The mean load required to dislodge the copings showed by synOcta abutments (11.19 kgf) was statiscally higher than s solid abutments (10.18 kgf).Conclusions: It was concluded that the abutment design influenced significantly the retention of metal copings.

Cementable implant crowns composed of cast superstructure frameworks luted to electroformed primary copings: an in vitro retention study

The aim of this in vitro study was to investigate, on ITI solid abutments, the retention values of single crowns fabricated using an alternative prosthetic solution: secondary cast superstructure luted to an electroformed primary coping. Fifty standard 4.1 mm ITI implants and 5.5 mm high ITI machined abutments were assembled and mounted in acrylic resin. Implant/abutment assemblies were randomly divided into two groups. In the test group, primary galvanic caps were directly fabricated on implant abutments (A.G.C. Micro machine), and a secondary cast noble alloy superstructure was luted on each primary galvanic cap with a resin cement (Nimetic Cem). In the control group, prefabricated burn-out caps were used for casting the metal frameworks. Test and control crowns were cemented using a resin cement (Panavia 21). After storage at 37 degrees for 24 h, the specimens were subjected to a pull-out test using an Instron universal testing machine. The load required to dislodge each sample and the respective mode of failure were recorded. Means and standard deviations of loads at failure were analyzed using ANOVA. Statistical significance was set at P< or =0.05. The retention values (+/-SD) of loads at failure were 67.26 (+/-16.61) for the test group and 44.03 (+/-9.45) for the control group. In the test group no separation occurred between the electroformed (galvanic) primary cap and the secondary superstructure. The results showed that this prosthetic solution is superior on retentive performance than the conventional cast framework. An added clinical advantage of this novel method is its potential to provide a totally passive fit. Further in vitro and in vivo studies involving multiple-unit restorations are needed in order to more generally validate this prosthetic concept.

Extraction of Weibull Parameters of Fiber Strength from Means and Standard Deviations of Failure Loads and Fiber Diameters

The errors in using an average fiber diameter to calculate the mean strength (ςm), Weibull reference strength (ς0), and Weibull modulus (m) from failure loads of fibers were examined experimentally. Although the use of an average diameter gave very good estimates of ςm, the error in the Weibull parameters (ς0 and m) was significant, which supported the recent simulation results. Computational approaches to reduce these errors have been considered, and a numerical procedure to extract the Weibull parameters from the means and standard deviations of the load and fiber diameter has been proven feasible, provided the sample population is large. Parametric studies have shown that sample populations of ∼175 are required to obtain results within an error of 10%. The recommended sample populations for commercial fibers are 75–200, depending on the scatter in the fiber diameter and the acceptable error.

Effect of soldering on metal-porcelain bond strength in repaired porcelain-fused-to-metal castings

Statement of problem. Chemical bonding plays a major role in the adherence between metal and porcelain. The formation of an oxide layer on solder material has not been described in the literature. It is unknown whether the application of solder negatively affects the bond strength between porcelain and metal.Purpose. This in vitro study assessed the effect of solder on the bond strength between metal and porcelain.Material and methods. Forty 20 × 6 × 0.5 mm patterns were divided into test (20) and control (20) groups. Test samples were perforated and repaired with solder, and 2 layers of opaque and dentin porcelain subsequently were applied on all samples. The samples were subjected to a 3-point flexural test on a screw-driven mechanical testing machine at a crosshead speed of 0.5 mm/min. Failure type (adhesive vs cohesive) was quantified by digitizing photographs of test and control samples. Three samples in each group also were examined with an SEM coupled with an x-ray energy-dispersive spectroscopy apparatus (SEM/EDS). Means and standard deviations of loads at failure, sample thickness, and surface area covered with porcelain were calculated, and data were analyzed with Student t test (P≤.05).Results. The mean fracture load for test samples was significantly greater than for control samples (P=.0038). Test samples also were significantly thicker (mean thickness difference 0.14 mm) (P=.0001). When the data were controlled for thickness by using a multiple linear regression analysis, no significant difference was found (P=.68). Test samples had a greater surface area covered with opaque porcelain (P=.0006) as determined by visual inspection.Conclusion. In this study, soldered and nonsoldered samples did not show any significant difference in porcelain-to-metal bond strength. Visual analysis revealed a significant difference in the amount of porcelain remaining on the fracture surface of the test and control samples; a complete quantitative elemental analysis with SEM/EDS is in progress. (J Prosthet Dent 2001;85:88-94.)

The ring cracking of glass by spherical indenters

T he W eibull statistical treatment of brittle strength is used to compute the mean fracture load and the standard deviation of fracture load for the ring cracking of glass by spherical indenters. An extension of the Weibull treatment allows the mean crack location also to be calculated. Predictions of mean load, standard deviation of load and mean crack location, all as a function of indenter radius, are made from material properties determined in bending tests. Good agreement is found with experiment over a wide range of indenter sizes.