Gamma Values Research Articles

Three-dimensional dose reconstruction-based pretreatment dosimetric verification in volumetric modulated arc therapy for prostate cancer.

PurposeWe performed three-dimensional (3D) dose reconstruction-based pretreatment verification to evaluate gamma analysis acceptance criteria in volumetric modulated arc therapy (VMAT) for prostate cancer.Materials and MethodsPretreatment verification for 28 VMAT plans for prostate cancer was performed using the COMPASS system with a dolphin detector. The 3D reconstructed dose distribution of the treatment planning system calculation (TC) was compared with that of COMPASS independent calculation (CC) and COMPASS reconstruction from the dolphin detector measurement (CR). Gamma results (gamma failure rate and average gamma value [GFR and γAvg]) and dose-volume histogram (DVH) deviations, 98%, 2% and mean dose-volume difference (DD98%, DD2% and DDmean), were evaluated. Gamma analyses were performed with two acceptance criteria, 2%/2 mm and 3%/3 mm.ResultsThe GFR in 2%/2 mm criteria were less than 8%, and those in 3%/3 mm criteria were less than 1% for all structures in comparisons between TC, CC, and CR. In the comparison between TC and CR, GFR and γAvg in 2%/2 mm criteria were significantly higher than those in 3%/3 mm criteria. The DVH deviations were within 2%, except for DDmean (%) for rectum and bladder.ConclusionsThe 3%/3 mm criteria were not strict enough to identify any discrepancies between planned and measured doses, and DVH deviations were less than 2% in most parameters. Therefore, gamma criteria of 2%/2 mm and DVH related parameters could be a useful tool for pretreatment verification for VMAT in prostate cancer.

Comparing climate adaptation strategies on technical efficiency of cassava production in Southwest, Nigeria

Purpose. The purpose of the article – to assess the technical efficiency of climate adaptation practices on cassava production in two different agro-ecological zones within the study area to know where the climate adaptation practices are more productive. To achieve the main objective of the study, the specific objectives were stated as follows: (a) describe relevant socio-economic characteristics of cassava farmers in southwestern region of Nigeria; (b) assess the influence of the used climate change adaptation strategies on technical efficiency of cassava production in both agro-ecological zones.
 Methodology / approach. The study was carried out in Ekiti, Osun and Oyo State in the southwestern region of Nigeria, where two different agro-ecological zones (AEZ) (rain forest and guinea savannah) were chosen for the study. The study used multi-stage sampling procedures, with well-structured questionnaire, to select 150 cassava producers from each AEZ, making a total of 300 cassava producers for the study. Data analysis was done using descriptive statistics and stochastic frontier production function.
 Results. From the study, it was revealed that cassava farmers in the study area were relatively young, fairly educated, mostly married, well experienced, adequately aware of climate change, but operated on a small scale. The result on the influence of climate adaptation strategies on technical efficiency of cassava production in both rain forest and savannah AEZs within the study area revealed that technical inefficiency existed in cassava production as confirmed by the gamma values of 0.687 and 0.639 in rain forest and savannah respectively
 Originality / scientific novelty. The study has really revealed diverse climate adaptation options available to cassava farmers in order to sustain its production as a means of employment to the unemployed, food consumption and contribution to the national gross domestic product. Studies comparing climate adaptation practices on the technical efficiency of cassava production in different agro-ecological zones in southwestern part of Nigeria are relatively scarce considering the mixture of socio-economic and climate variables to assess technical efficiency of cassava production.
 Practical value / implications. The study has succeeded in identifying key factors that will enables policy makers to formulate a sustained policy framework that would encourage the use of multiple climate adaptation practices by the cassava farmers. To ensure sustainability of cassava production, it is therefore recommended that farmers should use different adaptation strategies to climate change e.g crop diversification, multiple planting dates, land fragmentation, use of improved varieties and off farm income activities that would bring increase in their scale of operation as most of the cassava farmers in the study areas cultivated less than 2 hectares of land for cassava production.

Risk Assessments of Water Inrush from Coal Seam Floor during Deep Mining Using a Data Fusion Approach Based on Grey System Theory

With the increase in depth of coal mining, the hydrogeological complexity largely increases and water inrush accidents happen more frequently. For the safety of coal mining, horizontal directional drilling and grouting techniques have been implemented to detect and plug the fractures and conduits that deliver high-pressure groundwater to coal mine. Taking the grouting engineering performed at Xingdong coal mine at 980 m below sea level as an example, we collected the data of grouting quantity, the loss of drilling fluid, gamma value, water temperature, average water absorption, distance between grouting loss points, water pressure on coal seam floor, and aquifuge thickness at 90 boreholes in the mine to conduct grey relational analysis, first. The analysis showed that the grouting quantity was highly correlated with all other factors. Subsequently, grey system evaluation was used to evaluate the risk of water inrush from the coal seam floor. The results of risk analysis illustrated that three water inrushes from Ordovician limestone occurred in mining face 2127, 2125, and 2222 in the study area were all located in the area with a risk score higher than 65. Through grouting, the identified cracks were effectively blocked and waterproof layers beneath the coal seam floors were constructed to reduce the threat of water inrush. By comparing the risk assessment results with three water inrush cases before grouting operation, we found that water inrush areas were consistent with the area of higher risk.

Image contrast enhancement with brightness preservation using an optimal gamma and logarithmic approach

In this study, a new enhancement framework is proposed for low contrast and dark images where traditional histogram equalisation (HE), gamma and logarithmic transformation are incorporated to achieve a visually pleasing image. Before the operation of HE on the input image, gamma and logarithmic transformation are performed in order to preserve the fine details of the image. A new gamma value of the proposed algorithm helps to restrain histogram spikes to avoid over-enhancement and noise artefacts effect. After that, a novel logarithmic transformation is used to map a narrow range of low-intensity values in the input image to a wider range of output levels. Thus, the dark input values are spread out into the higher intensity values, which improve the overall contrast and brightness of the image. The proposed method is compared with various state-of-the-art techniques. The large dataset has been used to check the feasibility of the technique. The subjective and objective analysis shows that the proposed algorithm outperforms most of the existing contrast-enhancement algorithms and the results are natural-looking, good contrast images with almost no artefacts.

Optimal design of groundwater monitoring networks using gamma test theory

Gamma test theory (GTT) is introduced as a novel method to determine the optimal number and location of groundwater monitoring wells without requiring temporal monitoring data. This method is based on the calculation of a statistic, called gamma, for the data of one monitoring period. The optimal wells are selected such that while they have the lowest gamma value, a further increase in the number of wells does not cause much change in their gamma value. The method was applied to the design of an optimal monitoring network for groundwater electrical conductivity (EC) on Kish Island, Hormozgan Province, Iran. The water EC of 55 wells, selected from 244 existing wells, was measured during one monitoring period on Kish Island and their latitude and longitude were recorded. A groundwater EC monitoring network was optimized using a GTT-based optimization algorithm. Based on the results, to estimate the spatial distribution of groundwater EC on Kish Island with maximum achievable accuracy, it was necessary to monitor at least 110 wells, which were identified. Finally, the water EC of the proposed wells was monitored in three monitoring periods and the proposed network was evaluated in these periods. Results indicated that the proposed wells are also optimum in these periods and the spatial distribution of groundwater EC can be estimated with maximum achievable accuracy using the EC data of the proposed 110 wells. The current study provides a time- and cost-effective method to achieve an efficient groundwater monitoring network especially when there is data limitation.

An inverse error compensation method for color-fringe pattern profilometry

Color-fringe pattern profilometry is a widely used method for high-speed measuring 3D surface because the RGB (red, green and blue) channels provide more information. However, the nonlinear response of the digital projector usually causes periodical phase errors. In this paper, we analyze the nonlinear error in color-fringe pattern profilometry, and propose a multi-frequency fringe inverse error compensation method to reduce the phase error caused by the nonlinear response of the projector. The proposed method only needs to add one highest frequency RGB pattern, thus improving the measurement accuracy of color-fringe pattern profilometry. Different from other compensation methods, the proposed method does not need gamma calibration, the construction of a look-up-table of gamma values or many additional patterns, which are really time consuming. The experimental results demonstrated that the proposed method can effectively reduce the nonlinear effect of the projector and improve the measurement accuracy of color-fringe pattern profilometry.

Distinguishing Brans\u2013Dicke\u2013Kerr type naked singularities and black holes with their thin disk electromagnetic radiation properties

The possible existence of naked singularities, hypothetical astrophysical objects, characterized by a gravitational singularity without an event horizon is still an open problem in present day astrophysics. From an observational point of view distinguishing between astrophysical black holes and naked singularities also represents a major challenge. One possible way of differentiating naked singularities from black holes is through the comparative study of thin accretion disks properties around these different types of compact objects. In the present paper we continue the comparative investigation of accretion disk properties around axially-symmetric rotating geometries in Brans–Dicke theory in the presence of a massless scalar field. The solution of the field equations contains the Kerr metric as a particular case, and, depending on the numerical values of the model parameter gamma , has also solutions corresponding to non-trivial black holes and naked singularities, respectively. Due to the differences in the exterior geometries between black holes and Brans–Dicke–Kerr naked singularities, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution and equilibrium radiation spectrum) are different for these two classes of compact objects, consequently giving clear observational signatures that could discriminate between black holes and naked singularities.

A multi-institutional initiative on patient-related quality assurance: Independent computational dose verification of fluence-modulated treatment techniques

PurposeThis multi-institutional study investigates whether computational verification of fluence-modulated treatment plans using independent software with its own Strahlerkopfmodel is an appropriate method for patient-related quality assurance (PRQA) in the context of various combinations of linear accelerators (linacs), treatment techniques and treatment planning systems (TPS). Materials and methodsThe PRQA-software's (Mobius3D) recalculations of 9 institutions’ treatment plans were analyzed for a horseshoe-shaped planning target volume (PTV) inside a phantom. The recomputed dose distributions were compared to a) the dose distributions as calculated by all TPS's and b) the measured dose distributions, which were acquired using the same independent measuring system for all institutions. Furthermore, dose volume histograms were examined. The penumbra deviations and mean gamma values were quantified using Verisoft (PTW). Additionally, workflow requirements for computational verification were discussed. ResultsMobius3D is compatible with all examined TPSs, treatment techniques and linacs. The mean PTV dose differences (Mobius3D-TPS, <3.0%) and 3D gamma passing rates (>95.0%) led to a positive plan acceptance result in all cases. These results are similar to the outcome of the dosimetric measurements with one exception. The mean gamma values (<0.5) show a good agreement between Mobius3D and the TPS dose distributions. ConclusionUsing Mobius3D was proven to be an appropriate computational PRQA method for the tested combinations of linacs, treatment techniques and TPS's. The clinical use of Mobius3D has to be complemented with regular dosimetric measurements and thorough linac and TPS QA. Mobius3D's computational verification reduced measurement effort and personnel needs in comparison to dosimetric verifications.

Statistical Distribution of Rainfall in Kurdistan-Iraq Region

Study the statistical distribution for rainfall is important to know the behaviour of the rainfall series and to know the most frequently rainfall amount in each month. Five statistical distribution were applied on Sulaimani, Erbil and Duhok rainfall series for the period (1941-2017) except Duhok (1944-2017). These distributions were Gamma(3P), Weibul(3P), Earlang (3P), Normal and General extreme value. Kolmogrove-Semirnov, Anderson-Darling and Chi-Square goodness of fit test were used to know the best fit distribution from these five distributions.

Classification of Sulfadimidine and Sulfapyridine in Duck Meat by Surface Enhanced Raman Spectroscopy Combined with Principal Component Analysis and Support Vector Machine

In order to meet the growing demand for food safety, the rapid classification of sulfadimidine and sulfapyridine in duck meat based on surface-enhanced Raman spectroscopy (SERS) was investigated using gold nanoparticles (Au NPs) and NaCl solution as the active substrate and active agent, respectively. The results showed that the Raman characteristic peaks at 557 and 573 cm−1 were used to determine whether sulfadimidine and sulfapyridine remained in duck meat. A single factor experimental method was used to optimize the conditions. Three pretreatment methods were employed to optimize the raw measurements. According to the classification accuracies, adaptive iterative reweighted penalty least squares and second derivative were selected to be the optimal pretreatment method. Next, principal component analysis (PCA) was performed to extract the characteristic variables. The first four score values of PCA were selected to be the input values of support vector machine (SVM) classification model, which classified duck meat samples into four categories. Nu-support vector classification and radial basis function were selected to be the employed SVM classification model and the Kernel type, respectively. The gamma and nu values were 0.25 and 0.255, respectively. The classification accuracy for the test set was 90.44%. The sensitivities and specificities of test set were calculated, and the highest sensitivity and specificity values were 96.97% and 100%, respectively. The experimental results showed that this classification model provides favorable classification results. Therefore, the adopted method may be used for the rapid classification of sulfadimidine and sulfapyridine residues in duck meat.

Design, Fabrication, and Validation of a Polymethyl Methacrylate Head Phantom for Dosimetric Verification of Cranial Radiotherapy Treatment Plans.

Purpose:The present study aims to design and fabricate a novel, versatile, and cost-effective Polymethyl Methacrylate (PMMA) head phantom for the dosimetric pretreatment verification of radiotherapy (RT) treatment plans.Materials and Methods:The head phantom designing involves slice-wise modeling of an adult head using PMMA. The phantom has provisions to hold detectors such as ionization chambers of different sizes, Gafchromic films, gel dosimeter, and optically stimulated luminescence dosimeter. For the point dose verification purpose, 15 volumetric modulated arc therapy patient plans were selected, and doses were measured using a CC13 ionization chamber. The percentage gamma passing rate was calculated for acceptance criteria 3%/3 mm and 2%/2 mm using OmniPro I’mRT film QA software, and Gafchromic EBT3 films were used for 2D planar dose verification.Results:Treatment planning system calculated, and the measured point doses showed a percentage deviation ranged from 0.26 to 1.92. The planar dose fluence measurements, for set acceptance criteria of 3%/3 mm and 2%/2 mm, percentages of points having gamma value <1 were in the range of 99.17 ± 0.25 to 99.88 ± 0.15 and 93.16 ± 0.38 to 98.89 ± 0.23, respectively. Measured dose verification indices were within the acceptable limit.Conclusions:The dosimetric study reveals that head phantom can be used for routine pretreatment verification for the cranial RT, especially for stereotactic radiosurgery/RT as a part of patient-specific quality assurance. The presently fabricated and validated phantom is novel, versatile, and cost-effective, and many institutes can afford it.

Landslide susceptibility mapping by fuzzy gamma operator and GIS, a case study of a section of the national road n°11 linking Mateur to Béja (Nortshern Tunisia)

The purpose of this paper is to map the landslide susceptibility using the fuzzy gamma operator and GIS for the section of the national road n°11 linking Mateur to Beja. To minimize the subjectivity of the fuzzy logic approach, the frequency ratio was used to calculate the fuzzy membership. To locate the 147 landslides, Google Earth extracts analysis, and field survey has been done. In this cartography, nine factors controlling landslides were used: slope, aspect, curvature plane, curvature profile, distance to faults, distance to rivers, land use, rainfall, and lithology. Once the fuzziness is calculated in each factor using the frequency ratio (FR), the fuzzy gamma operator can be applied to these nine factors to produce the landslide susceptibility map. Finally, the choice of the nearest susceptibility map of reality is made by applying the ROC curve. By the analysis of the area under curve (AUC), it is seen that the prediction accuracy of model proves that the gamma value of 0.90 yielded the better prediction of landslide susceptibility map (0.89). Finally, our area of interest was classified based on the Jenks natural breaks classification method into five classes, such as non-susceptible zone, low susceptible zone, moderate susceptible zone, high susceptible zone, and very high susceptible zone. Landslide susceptibility mapping based on the fuzzy gamma operator presents a very acceptable result with a reliability of 89%.

Methylene Diphosphonate Bone Scan Scintigraphic Image Enhancement using Gamma Correction and Optimizing the Value of Gamma.

Introduction:Focal areas of high radiotracer uptake in a bone-scan image can result in dynamic range of the intensity value to exceed the dynamic range of the display, requiring multiple interactive contrast adjustments. This unnecessary burden on time of physician can be avoided using power law equation to brighten up the low-intensity areas in image. However, despite the widespread availability of this technique in commercial systems, for this clinical setting, the gamma-value needs to be standardized.Materials and Methods:Sixty dark bone scan images were selected. Ten randomly selected images from this set were evaluated qualitatively and quantitatively (perception-based image quality evaluator, absolute mean brightness error, structural similarity, and peak signal to noise ratio) to select a range of gamma values (from 0.1 to 0.9, increment of 0.1), where the results were acceptable. This range of gamma was then applied to rest of the 50 images to find the best value. Images were evaluated by two experienced nuclear medicine physicians. Although not ideal, but for the purpose of simplicity, we tried reaching a single best value. For this, the physicians were asked to reach consensus on the acceptable images.Results:In the first part of the study, after evaluation of 100 images (1 original and 9 processed images with 0.1–0.9 gammas), range of gamma values from 0.3 to 0.8 was found to be optimum. This range was then applied to rest of the 50 images. Evaluation of resultant 350 images (1 original and 6 processed for each input image) further narrowed this range to 0.4–0.7 (0.3 gamma selected only twice by one physician). The kappa for acceptable images was moderate at 0.482 (P <0.001). The single gamma value of 0.6 resulted in 72% of the images to be acceptable.Conclusion:Use of power law equation to brighten up the low intensity areas of dark bone scan images, without loss of clinically significant details, is feasible with single gamma value of 0.6 and range of 0.4–0.7 giving best results.

The impact of organizational culture on innovation for the development of tourism SMEs in the municipality of Caborca, Sonora

The results presented in this study related the factor of organizational culture with innovation for the development of small tourist businesses (SMEs) in the municipality of Caborca, Sonora. For which an exploratory analysis of the model, was made to subsequently analyze the Association of variables through the model of the Chi-square and thus be able to check the predictive and explanatory power of the same by means of Probit and Logit analysis. The collection of data was used as measurement instrument a structured questionnaire was administered to managers or entrepreneurs of tourism SMEs in the municipality of Caborca, Sonora. Where was the reliability of the instrument for measuring, the R² and significance of the model Chi square statistical analysis was used to identify the relationship and association between the variables of the proposed model, obtaining the coefficient Gamma with a strong correlation between the variables, as well as Gamma, Probit and Logit values, acceptable values for the relationship between the dependent variable and the independent variable was observed. A higher rate and robustness of prediction of the variables with acceptable significance was also obtained.

Prevalence of latent tuberculosis infection in healthcare workers in tertiary care hospitals of Pakistan.

Objective:To determine the prevalence of latent tuberculosis infection (LTBI) in healthcare workers in tertiary care hospitals of Rawalpindi, using interferon gamma release assay.Methods:It was a cross-sectional study. The samples were collected from pulmonology and microbiology departments of three hospitals; i) Military Hospital, Rawalpindi, ii) Fauji Foundation Hospital, Rawalpindi and iii) Pakistan Institute of Medical Sciences, Islamabad. The study was completed in one year from January 2017 to January 2018. Fifty-five asymptomatic healthcare workers of both genders between the ages of 18-50 years with a working tenure of at least one year in concerned departments were included and those with active tuberculosis were excluded from the study. Whole blood from subjects was collected and plasma was checked for interferon gamma value by IGRA (Interferon gamma release assay).Results:In this study of total 55 healthcare workers a high prevalence 22 (40.0%) of latent tuberculosis was found. When LTBI distribution was analyzed within occupational categories, the most frequently affected were sanitary workers 3 (100.0%), nurses 5 (50.0%), doctors 6 (43%) and nursing assistants 2 (40%).Conclusion:The prevalence of LTBI in healthcare workers is alarmingly high in our local healthcare settings.

Radiometric and petrographic characterization of sediment samples collected from Jhelum, Neelum and Kunhar Rivers of Muzaffarabad, Azad Kashmir

In the present study, we present results of radiometric and petrographic analyses of sediment samples collected from the river banks of Jhelum, Neelum, and Kunhar confluencing in the district Muzaffarabad. Gamma activity concentrations due to 226Ra, 232Th, and 40K were determined using high-purity germanium detector (HPGe). For a total of thirty sediment samples collected from three rivers, the activity concentrations of 226Ra, 232Th and 40K varied from 03.32 ± 0.40 to 100.45 ± 2.08 Bq Kg−1, 02.17 ± 1.35 to 298.42 ± 4.50 Bq Kg−1 and 37.88 ± 11.66 to 1386.32 ± 30.17 Bq Kg−1 with mean values of 36.91 ± 1.12, 61.57 ± 2.81 and 557.33 ± 19.81 Bq Kg−1, respectively. The overall value of Raeq for all the investigated sediment samples was found to be in the range from 9.34 ± 3.23 to 633.53 ± 10.14 Bq Kg−1 with mean value of 167.88 ± 6.66 Bq Kg−1. The values estimated for hazard indices, viz., external hazard index (Hex), internal hazard index (Hin), representative index (Ir), gamma index (I) and alpha index (Iα) for all sediment samples were found to be in the range from 0.02 ± 0.008 to 1.71 ± 0.03, 0.034 ± 0.009 to 1.98 ± 0.03, 0.07 ± 0.02 to 4.57 ± 0.07, 0.03 ± 0.01 to 2.29 ± 0.03 and 0.02 ± 0.002 to 0.50 ± 0.010 with mean values of 0.45 ± 0.02, 0.55 ± 0.02, 1.23 ± 0.04, 0.62 ± 0.02 and 0.18 ± 0.010, respectively. The activity concentrations were subsequently used to estimate the terrestrial gamma ray absorbed dose rate in air at 1 m above the ground and annual effective dose. For all the samples, the values of gamma absorbed dose rate and annual effective dose ranged from 4.42 ± 1.49 to 284.24 ± 4.64 nGyh−1 and 0.027 ± 0.009 to 1.74 ± 0.03 mSv year−1 with mean values of 77.49 ± 3.04 nGyh−1 and 0.48 ± 0.02 mSv year−1, respectively. Mean gamma absorbed dose rate computed in the present study is higher than that reported for world average (59 nGy h−1) and it also exceeds the UNSCEAR proposed safe limit of 55 nGyh−1. The resulting annual effective dose is also higher than the worldwide average value of 0.07 mSv year−1, however, it is less than the safe limit of 1 mSv year−1. From the present study, it is concluded that there is a possibility of high radiation risk from the sediments of the surveyed rivers due to elevated activity concentrations and doses when used as building materials. The building codes need to be revisited taking into account the effects of radiation exposure and absorbed dose on the inhabitants.

Türkmendağı orman vejetasyonu ve bitki çeşitliliği ile bazı yetişme ortamı faktörleri arasındaki ilişkiler (Eskişehir-Kütahya, Türkiye)

The aim of this study is to determine the vascular plant diversity of forest vegetation in Türkmendağ and to reveal vegetation-environmental relationships. The sampling was done using the Braun-Blanquet method in 95 grids. Two subplots were sampled in each grid. Plant groups were determined by hierarchical classification clustering analysis. The relations between plant groups and environmental variables were examined by non-parametric test statistics. Alpha, beta and gamma (α, β, γ) values, which are the species diversity indices of plant groups and sample areas were calculated. The interrelationships among the diversity components (α, βw and γ) of the sample areas, and the site factors were analysed by regression tree method. The best regression tree model was built by tree layer, shrub layer, slope, RI, limestone and altitude respectively. According to statistical analysis, the same variables played dominant roles for the distribution of plant groups. When we evaluate all three plant species diversity components together, plant groups endowed with the highest species diversity are Group 1, Group 2, Group 4 and Group 8.

The Naples Systematic Series – Second part: Irregular waves, seakeeping in head sea

The main aim of this study is to characterize the dynamic behavior of the Naples Systematic Series (NSS) in irregular head sea. A further aim of the study is to provide data to detect the influence of hull form on the sea-keeping performances in the planing and semi-planing speed range.The NSS derives from a parent hull that has shown to behave well in rough seas, characterized by high deadrise angles of the bottom at the bow, to reduce acceleration. All the models of NSS were tested in three different sea states and in Fr range from 0.515 to 1.197. The relatively high Froude numbers associated with the forms of the series make inappropriate the statistical analysis usually carried out to describe the behavior of the displacement ships.To overcome these unsuitableness, Cartwright Lounguet Higgins, extreme value and normal distribution fittings have been furnished for heave and pitch maxima and minima; gamma and extreme value have been furnished to represent acceleration in the centre of gravity and bow.Finally, a case study is presented to show a useful procedure for designer evaluation.

Global Asset Allocation Strategy Using a Hidden Markov Model

This study uses the hidden Markov model (HMM) to identify the phases of individual assets and proposes an investment strategy using price trends effectively. We conducted empirical analysis for 15 years from January 2004 to December 2018 on universes of global assets divided into 10 classes and the more detailed 22 classes. Both universes have been shown to have superior performance in strategy using HMM in common. By examining the change in the weight of the portfolio, the weight change between the asset classes occurs dynamically. This shows that HMM increases the weight of stocks when stock price rises and increases the weight of bonds when stock price falls. As a result of analyzing the performance, it was shown that the HMM effectively reflects the asset selection effect in Jensen’s alpha, Fama’s Net Selectivity and Treynor-Mazuy model. In addition, the strategy of the HMM has positive gamma value even in the Treynor-Mazuy model. Ultimately, HMM is expected to enable stable management compared to existing momentum strategies by having asset selection effect and market forecasting ability.

Flexible gamma calculation algorithm based on probability distribution function in digital fringe projection system.

The gamma effect of phase-measuring profilometry systems yields nonlinear errors, which will substantially reduce the 3D shape measurement accuracy. Here, a robust and flexible gamma correction method based on the probability distribution function (PDF) of the wrapped phase is presented. First, a series of PDF curves are generated from the simulated wrapped phase distributions with different gamma values. Second, an experimental PDF curve will be produced after obtaining the wrapped phase from the captured three-step phase-shift fringe images. Then, a correlation procedure will be used to find the most similar PDF curve from the simulated PDF curves, and the gamma value of the matched PDF curve is that of the current system. Note that the gamma value detected by this method will be smaller than the true value due to the defocusing effect of the projection system with a large aperture. Therefore, an improved PDF-based algorithm, which projects two sets of three-step phase-shifting sinusoidal fringe patterns with different pre-coded gamma values and produces two PDF curves, is also added. Then after one more correlation procedure, a more accurate systematic gamma value could be calculated. It does not need large-step phase-shift images and 2×3 fringe images are quite enough. The experimental results show that the technique is very fast, easy to use and quite accurate.