Strength and deformation characteristics of irregular columnar jointed rock mass: A combined experimental and theoretical study

The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of CJRM is important for engineering construction.The Voronoi diagram and three-dimensional printing technology were used to make an irregular columnar jointed mold,and the irregular CJRM(ICJRM)specimens with different dip directions and dip angles were prepared.Uniaxial compression tests were performed,and the anisotropic strength and deformation characteristics of ICJRM were described.The failure modes and mechanisms were revealed in accordance with the final appearances of the ICJRM specimens.Based on the model test results,the empirical correlations for determining the field deformation and strength parameters of CJRM were derived using the dip angle and modified joint factor.The proposed empirical equations were used in the Baihetan Project,and the calculated mechanical parameters were compared with the field test results and those obtained from the tunneling quality index method.Results showed that the deformation parameters determined by the two proposed methods are all consistent with the field test results,and these two methods can also estimate the strength parameters effectively.

Reinforcement Method of the Tubular Joints under Combined Loads Based on ANSYS Software

The jacket offshore platform structures working in the environment are subjected to various external conditions,such as wave loads,wind loads and corrosion of sea water.Therefore,the research on reinforcement of tubular joints has great practical value for the safety of offshore platforms.In this article,the finite element(FE)models of T-type tubular joint(T-joint)and K-type tubular joint(K-joint)are established by ANSYS software.Triangular rib reinforcement and collar plate reinforcement are used to reinforce the tubular joints.The reinforcement effects are assessed through the ultimate bearing capacity,and the influences of parameters of the rib and the collar plate on the ultimate capacity are analyzed.Besides,the effects of the two reinforcement methods are compared under the combined loads,and the results show that the reinforcement of the ribbed plate is more effective in resisting the deformation caused by bending moment,while the reinforcement of the collar plate is more effective to avoid the plastic damage caused by the axial pressure.

Meta-analysis of the efficacy and safety of combined surgery in the management of eyes with coexisting cataract and open angle glaucoma

AIM： To conduct a systematic review and quantitative Meta-analysis of the efficacy and safety of combined surgery for the eyes with coexisting cataract and open angle glaucoma.METHODS： We performed a systematic search of the related literature in the Cochrane Library, PubM ed, EMBASE, Web of Science databases, CNKI, CBM and Wan Fang databases, with no limitations on language or publication date. The primary efficacy estimate was identified by weighted mean difference of the percentage of intraocular pressure reduction（IOPR%） from baseline to end-point, the percentage of number of glaucoma medications reduction from pre-to post-operation, and the secondary efficacy evaluations were performed by odds ratio（OR） and 95% confidence interval（CI） for complete and qualified success rate. Besides, ORs were applied to assess the tolerability of adverse incidents. Meta-analyses of fixed or random effect models were performed using Rev Man software 5.2 to gather the consequences. Heterogeneity was evaluated by Chi^2 test and the I^2 measure.RESULTS： Ten studies enrolling 3108 patients were included. The combined consequences indicated that both glaucoma and combined cataract and glaucoma surgery significantly decreased IOP. For deep sclerectomy vs deep sclerectomy plus phacoemulsification and canaloplasty vs phaco-canaloplasty, the differences in IOPR% were not all statistically significant while trabeculotomy was detected to gain a quantitatively greater IOPR% compared with trabeculotomy plus phacoemulsification. Furthermore, there was no statistical significance in the complete and qualified success rate, and the rates of adverse incidents for trabeculotomy vs trabeculotomy plus phacoemulsification.CONCLUSION： Compared with trabeculotomy plus phacoemulsification, trabeculectomy alone is more effective in lowering IOP and the number of glaucoma medications, while the two surgeries can not demonstrate statistical differences in the complete success rate, qualified success rate, or incidence of adverse incidents.

Rock burst mechanism analysis in an advanced segment of gob-side entry under different dip angles of the seam and prevention technology

In order to investigate the frequent occurrences of rock burst in gob-side entry during the mining process of the mining zone No. 7, the mechanical model of main roof of fully-mechanized caving mining before breaking was established by the Winkler foundation beam theory, and the stress evolution law of surrounding rock with different dip angles of the seam during the mining process was analyzed by using FLAC3 D. The results show that: with the dip angle changing from 45° to 0°, the solid-coal side of gobside entry begins to form an L-shaped stress concentration zone at a dip angle of 30°, and the stress concentration degree goes to higher and higher levels. However, the stress concentration degree of the coalpillar side goes to lower and lower levels; the influence range and peak stress of the abutment at the lateral strata of adjacent gob increase with dip angle decreasing and reach a maximum value at a dip angle of 0°, but the tailgate is not affected; the abutment pressure superposition of two adjacent gobs leads to stress concentration further enhancing in both sides of gob-side entry. With the influence of strong mining disturbance, rock burst is easily induced by dynamic and static combined load in the advanced segment of gob-side entry. To achieve stability control similar to that in the roadway, the key control strategy is to reinforce surrounding rock and unload both sides. Accordingly, the large-diameter drilling and high-pressure water injection combined unloading and reinforced support cooperative control technology was proposed and applied in field test. The results of Electromagnetic Emission(EME) and field observation showed that unloading and surrounding rock control effect was obvious.

Fixed combination of latanoprost and timolol vs the individual components for primary open angle glaucoma and ocular hypertension:a systematic review and meta-analysis

AIM:To assess the effects of the fixed combination of0.005% latanoprost and 0.5% timolol(FCLT) vs their individual components for primary open angle glaucoma(POAG) and ocular hypertension(OHT).· METHODS:After searched PubMed, EMBASE, the Cochrane Library and SCI, all randomized controlled clinical trials(RCTs) and cross-over studies were included. The control groups were the monotherapy or the concomitant therapy of latanoprost and timolol. The outcomes were visual field defect, optic atrophy, mean intraocular pressure(IOP) and IOP fluctuation. The analysis was carried out in RevMan version 5.1 software.RESULTS:Thepost-interventionmeanIOPofFCLTwas significantly lower compared to timolol [mean difference(MD)-2.92, 95%CI-3.28 to-2.55, P 【0.00001] and latanoprost(MD-1.11, 95%CI-1.51 to-0.72, P 【0.00001). The postintervention IOP fluctuation was also significantly lower compared to timolol(MD-0.88, 95%CI-1.23 to-0.53, P 【0. 00001) and latanoprost( MD- 0. 63, 95 % CI- 1. 04to-0.22, P =0.002). The mean IOP was higher in FCLT morning dose group than the one in unfixed combination of 0.005% latanoprost and 0.5% timolol(UFCLT)(MD1.10, 95% CI 0.81 to 1.39, P 【0.00001). Otherwise, there was no difference between FCLT evening dose group and UFCLT(MD 0.34, 95% CI-0.01 to 0.69, P =0.06).There was no statistical difference for the incidence ofvisual field defect and optic atrophy between FCLT and the monotherapy of components.CONCLUSION:A better IOP lowering effect has been demonstrated for FCLT compared to the monotherapy of components. The IOP lowering effect was worse for FCLT morning dose and almost same for FCLT evening dose compared to the UFCLT. We need more long-term high quality RCTs to demonstrate the outcomes of visual field defect and optic atrophy.visual field defect and optic atrophy between FCLT and the monotherapy of components.CONCLUSION:A better IOP lowering effect has been demonstrated for FCLT compared to the monotherapy of components. The IOP lowering effect was worse for FCLT morning dose and almost same for FCLT evening dose compared to the UFCLT. We need more long-term high quality RCTs to demonstrate the outcomes of visual field defect and optic atrophy.

Determining relative block structure rating for rock erodibility evaluation in the case of non-orthogonal joint sets

The most commonly used method for assessing the hydraulic erodibility of rock is Annandale's method.This method is based on a correlation between the erosive force of flowing water and the capacity of rock resistance. This capacity is evaluated using Kirsten's index, which was initially developed to evaluate the excavatability of earth materials. For rocky material, this index is determined according to certain geomechanical factors related to intact rock and rock mass, such as compressive strength of intact rock, rock block size, discontinuity shear strength and relative block structure. To quantify the relative block structure, Kirsten(1982) developed a mathematical expression that accounts for the shape and orientation of the blocks relative to the direction of flow. Kirsten's initial concept for assessing the relative block structure considers that the geological formation is mainly fractured by two joint sets forming an orthogonally fractured system. An adjusted concept is proposed to determine the relative block structure when the fractured system is non-orthogonal where the angle between the planes of the two joint sets is greater or less than 90°. An analysis of the proposed relative block structure rating shows that considering a non-orthogonally fractured system has a significant effect on Kirsten's index and, as a consequence, on the assessment of the hydraulic erodibility of rock.

Analysis of the influence of joint characteristic parameters on roadway deformations

By means of numerical simulation, the roadway deformation affected by joints was analyzed and the pre-tensioned bolts for reinforcing roadway roof in jointed rock mass was studied. The results show that the roadway roof deformation increases gradually with the accretion of joint length, the increase of joint number, the de- crease of intervals, angles and friction angles of joints. The increase is obvious at beginning and then tends slowly. After pre-tensioned bolts are used, roadway roof deformations reduce obviously, and the supporting action of pre-tensioned bolts is more remarkable with accretion of joint length, increasing of joint number, reducing of joint interval, decreasing of joints angle and joint friction angle, and increasing of joint number that bolts drilling through. With comparison of different cases, the joints supporting effect is more remarkable at a small angel. It indicates that the supporting mechanism of pre-tensioned bolts is to reinforce weak faces, such as joints. The more joints the roof includes, the more visible the pre-tensioned bolts strengthening effect is.

Combination of structure tensor and tilt angle in the edge detection of potential field data

Edge detection is a commonly requested task in the interpretation of potential field data. Different methods have different results for varied depths and shapes of geological bodies. In this paper,we propose using the combination of structure tensor and tilt angle to detect the edges of the sources,which can display the edges of shallow and deep bodies simultaneously. Through tests on synthetic potential field data,it is obvious that the proposed edge detection methods can display the sources edges more clearly and precisely,compared with other commonly used methods. The application on real potential field data shows similar result,obtaining the edges of layers and faults clearly. In addition,another advantage of the new method is its insensitivity to noise.

A comparative study on imaging parameters of Chevron combined with Akin osteotomy and Scarf combined with Akin osteotomy for the correction of hallux valgus in patients at different ages

Objective:To study the imaging parameters of Chevron combined with Akin and Scarf combined with Akin for the correction of hallux valgus in patients of different ages.Methods:Eighty patients(152 feet)with hallux valgus who underwent Chevron combined with Akin and Scarf combined with Akin in our hospital were randomly selected.The patients were divided into young and middle-aged groups.Measure the hallux valgus angles(HVA),distal metatarsal articular angle(DMAA)and intermetatarsal angles(IMA)with professional X-ray measurement software and then reseach the effect of two the operation methods.Results:Young group:Chevron combined with Akin and Scarf combined with Akin significantly improved HVA and IMA,the difference had statistical significance(P<0.05),but the improvement effect of the two groups was similar,and the difference had no statistical significance(P>0.05).The improvement effect of the two groups on DMAA in young patients was not significant,and the difference had no statistical significance(P>0.05);Middle-aged group:Chevron combined with Akin and Scarf combined with Akin also significantly improved HVA and IMA(P<0.05),but the improvement effect of the two groups was similar,and the difference had no statistical significance(P>0.05).Chevron combined with Akin significantly improved DMAA in middle-aged and elderly patients,and the difference had statistical significance(P<0.05).Scarf combined with Akin did not significantly improve DMAA in middle-aged and elderly patients,and the difference had no statistical significance(P<0.05).Conclusion:Both Chevron combined with Akin and Scarf combined with Akin are effective and widely used.Chevron combined with Akin was able to improve DMAA in middle-aged and elderly patients.Therefore,Chevron combined with Akin is recommended for middle-aged and elderly patients with hallux valgus.

Effect of bolt inclination angle on shear behavior ofbolted joints under CNL and CNS conditions

Rock bolts are widely used in rock engineering projects to improve the shear capacity of the jointed rock mass.The bolt inclination angle with respect to the shear plane has a remarkable influence on the bolting performance.In this study,a new artificial molding method based on 3D scanning and printing technology was first proposed to prepare bolted joints with an inclined bolt.Then,the effects of the bolt inclination angle and boundary conditions on the shear behavior and failure characteristic of bolted joints were addressed by conducting direct shear tests under both CNL and CNS conditions.Results indicated that rock bolt could significantly improve the shear behavior of rock joints,especially in the post-yield deformation region.With the increase of bolt inclination angle,both the maximum shear stress and the maximum friction coefficient increased first and then decreased,while the maximum normal displacement decreased monotonously.Compared with CNL conditions,the maximum shear stress was larger,whereas the maximum normal displacement and friction coefficient were smaller under the CNS conditions.Furthermore,more asperity damage was observed under the CNS conditions due to the increased normal stress on the shear plane.

Shear mechanical properties and fracturing responses of layered rough jointed rock-like materials

This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear loading.Cubic layered samples with dimensions of 100 mm×100 mm×100 mm were casted using rock-like materials,with anisotropic angle(α)and joint roughness coefficient(JRC)ranging from 15°to 75°and 2-20,respectively.The direct shear tests were conducted under the application of initial normal stress(σ_(n)) ranging from 1-4 MPa.The test results indicate significant differences in mechanical properties,acoustic emission(AE)responses,maximum principal strain fields,and ultimate failure modes of layered samples under different test conditions.The peak stress increases with the increasingαand achieves a maximum value atα=60°or 75°.As σ_(n) increases,the peak stress shows an increasing trend,with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares fitting.As JRC increases from 2-4 to 18-20,the cohesion increases by 86.32%whenα=15°,while the cohesion decreases by 27.93%whenα=75°.The differences in roughness characteristics of shear failure surface induced byαresult in anisotropic post-peak AE responses,which is characterized by active AE signals whenαis small and quiet AE signals for a largeα.For a given JRC=6-8 andσ_(n)=1 MPa,asαincreases,the accumulative AE counts increase by 224.31%(αincreased from 15°to 60°),and then decrease by 14.68%(αincreased from 60°to 75°).The shear failure surface is formed along the weak interlayer whenα=15°and penetrates the layered matrix whenα=60°.Whenα=15°,as σ_(n) increases,the adjacent weak interlayer induces a change in the direction of tensile cracks propagation,resulting in a stepped pattern of cracks distribution.The increase in JRC intensifies roughness characteristics of shear failure surface for a smallα,however,it is not pronounced for a largeα.The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered rocks subjected to shear loads.

Efficacy of Combined Administration of 0.2% Brimonidine and 0.5% Betaxolol in Treatment of Primary Open Angle Glaucoma and Ocular Hypertension

Purpose:To observe the efficacy of combined use of brimonidine and betaxolol in treatment of primary open angle glaucoma(POAG)and ocular hypertension.Methods:A total of 54 patients(90 eyes)with POAG and ocular hypertension were randomly divided into three groups(receiving betaxolol,.brimonidine and combined administration of betaxolol and brimonidine respectively).The administration was given twice daily in all groups(0.5%betaxolol,0.2%brimonidine and 0.5%betaxolol combined with 0.2%brimonidine).The changes in intraocular pressure(IOP)were observed before,and 2,4,6,and 8 weeks after treatment.In addition,the adverse reactions were also recorded post-treatment.Results:.The mean IOPs at all the time points after treatment were significantly reduced compared with pre-treatment levels(P<0.05).Patients receiving brimonidine had a greater reduction in IOP compared with their counterparts in the betaxolol group but the difference was not statistically significant.The IOP decline was significantly higher in the combined therapy group than in the other two groups(P<0.01).Few cases presented with slight discomfort,.such as sensation of foreign bodies,.ocular irritation,.dizziness,.headache,.fatigue,.and dryness of mouth and nose.No severe adverse reactions were noted following administration.Conclusion:Combined use of brimonidine and betaxolol is an efficacious treatment of reducing IOP without severe side effects.

Numerical study on the separation and superposition of the influences from up-and downstream rotors

A three-dimensional Navier-Stokes solver is used to investigate the separation and superposition of the influences from upstream and downstream rotors in an axial-radial combined compressor for unsteady design applications. The data from rotor/stator and stator/rotor configurations show that the unsteady flow response in axial stator passage is caused only by one rotor. The results from the rotor/stator/rotor configuration revealed the superimposed characteristic of influences from upstream and downstream the rotor. The impact of the superimposed characteristic was studied by analyzing the virtual relative flow angle at the stator exit. The results show that the axial velocity in the passage of axial stator can be influenced by wake from upstream axial rotor and potential field of downstream radial rotor. While they are coupled to have an effect on the unsteady flow in axial statot passage, the excitation or suppression phenomena appear and lead to different levels of deterministic fluctuation kinetic energy. Their locations are determined by the frequencies of the involved influences. In addition, the variability of superimposed characteristic （ excitation and suppression） at the stator exit modulates the inlet flow angle for downstream rotor.

Combined Cycle Fatigue Testing with Ultrasonic FrequencyComponent of S350 Steel Welded Joint

A combined cycle fatigue （CCF） testing system with ultrasonic frequency component was developed toevaluate the CCF properties of S350 steel welded joints in this study. The fatigue testing results indicated that the S-Ncurves of CCF did not have fatigue limit, which agreed with those of pure high frequency fatigue of welded joints. TheS-N curves showed that the CCF strength of welded joints dropped greatly with the increasing interaction between highand low frequency fatigue loading. An approximation design method of CCF was presented using amplitude envelopeas the stress range.

Long-term assessment of prostaglandin analogs and timolol fixed combinations vs prostaglandin analogs monotherapy

AIM： To draw a Meta-analysis over the comparison of the intraocular pressure （lOP）-lowering efficacy and safety between the commonly used fixed-combinations of prostaglandin analogs and 0.5% timolol with prostaglandin analogs （PGAs） monotherapy. METHODS： After searching the published reports from MEDLINE, EMBASE, the Cochrane Library, all randomized controlled clinical trials （RCTs） comparing the fixed combination of PGAs/timolol therapy （FCs） and PGAs monotherapy with treatment duration at least 6mo were included. The efficacy outcomes were mean diurnal lOP, percentage of participants whose lOP were lower than 18 mm Hg, incidence of visual field change, while the safety outcomes included corneal side effects, hyperemia and eye irritation. The analysis was carried out in RevMan version 5.3 software. RESULTS： After six-month medical intervention, the mean diurnal lOP of FCs was lower than PGAs （MD -1.14, 95% CI -1.82 to -0.46, P=0.001）; the percentage of target lOP achieving between FCs and PGAs showed no significant difference （RR 1.18, 95% Cl 0.97 to 1.43, P=0.10）. No statistically significant differences of the incidence of hyperemia （RR 0.67, 95% CI 0.45 to 1.01, p=0.06） and eye irritation （RR 1.20, 95% CI 0.95 to 1.51, P=0.12） between the FCs and PGAs monotherapy were detected. Only one research involved in corneal events, result of this trial revealed no difference between two intervention groups regarding corneal effects （central endothelial cell density, MD -0.20, 95% CI -0.72 to 0.32, P=0.45; central corneal thickness, MD -0.01, 95% Cl -0.02 to 0.00, P=0.23）. The evaluation of visual field change was not performed due to the limited duration of the trials included in this Meta-analysis. CONCLUSION： The long-term efficacy of the FCs overweighed the PGAs monotherapy in lowering lOP, but in the incidence of hyperemia and eye irritation syndromes, the differences are not statically significant. More RCTs with detailed and authentic data over the assessments of visual functions and morphology of optic nerve heads are hoped to be conducted.

Experimental Study and Finite Element Analysis on Ultimate Strength of Dual-Angle Cross Combined Section Under Compression

This paper investigates Q420 dual-angle cross combined section columns under axial and eccentric compression by conducting experiments.The specimen parameters,experimental setup,and test results are presented.It showed that local buckling occurred apparently for single internode specimens(λ<35)under axial compression,while overall bending buckling appeared for others,and no torsional buckling occurred.The theoretical formulas on stability factor were derived by the energy approach.Non-linear finite element models considering residual stress were established using ANSYS which were verified by the corresponding experimental results.The parametric study was to evaluate the effects of slenderness ratio(λ),width to thickness ratio of angles(b/t),the number of filled plate(n),load relative eccentricity(e)and the lateral support stiffness on the ultimate strengths of dual-angle cross combined section columns.Based on above analysis,the design equations are proposed by using curve fitting technique.It is shown from comparison between test results,finite element analysis and related specifications that the ultimate strength from theoretical formulas,proposed equations and finite element models are consistent with experiments results.

Theory of pleiotropic action of biologically active compounds and medicines—Basic principles and practical application

This article represents the main positions of the theory of pleiotropic action of biologically active compounds (BACs) and medicines, which has been designed by the author based on her own experimental researches. The term “pleiotropy” means the ability of the BACs and medicines to implement more than one mechanism of action resulting in the specific biological (pharmacological) effect. The interaction of these mechanisms forms a distinct pattern of biological response (pleiotropic pattern), which reflects the change in his character with the increased dose (concentration)-dependent efficacy of BACs and medicines. The article consists of description of different pleiotropic patterns established in experiments on the model of reactive oxygen species (ROS) generation by macrophages dependent on activity of specialized enzyme called Nox2-NAD(P)H oxidase (Nox2, EC 1.6.3.1). Moreover, it consists of explanation of pharmacodynamic nature of pleiotropic patterns by means of application Chou-Talalay median effect equalization and combination index (CI) theory. The novel theory explains unsolved until now universal aspects of activity BACs and medicines, such as slope angles of “dose-effect” dependences in the conditions relevant in vivo, and it is of fundamental interest. However, it has applications in experimental pharmacology, as it allows defining the choice of the individual compounds and combinations, modulating the trust effect selectively and efficiently. This knowledge opens up new approaches to medicines discovery and evaluation, their rational dosing and combining.

Estimation of 2-D Angles of Arrival Based on Joint Diagonalization of Two Spatio-Temporal Correlation Matrices

In this paper, we propose a two-dimensional （2-D） angles of arrival （AOAs） estimation method based on a joint diagonalization of two spatio-temporal （ST） correlation matrices. The mathematical manipulations proposed in this paper take the structure of the array that enable estimating 2-D AOAs simultaneously without 2-D searching or pairing. The performance comparison shows that the proposed method is better than ST-DOA matrix method.

Analysis on Genetic Characteristics of Leaf Angle in Waxy Corn

The leaf angle in waxy corn is a significant trait for breeding corn with compact plant type, which is beneficial to improve yield. According to the Griffing method II, the GCA （general combining ability） and SCA （specific combining ability） of leaf angle trait in the 7 waxy corn inbred lines and 21 combinations were esti-mated, and the genetic characteristics of leaf angle in corn were also analyzed. The results showed that among the 7 inbred lines, the GCA values ranked as N22 〉N8 〉 N28 〉 N7 〉 N23 〉 N27 〉 N4. The GCA of N27 showed great negative ef-fect, and the genetic variance of its SCA was lower. It suggested that the N27 can be used as an ideal parent for breeding excel ent combinations with smal leaf angle and compact plant type. The inheritance of leaf angle trait in waxy corn is in ac-cordance with the model of ＂additive - dominant - epistatic＂. The efficiency of leaf angle trait is control ed by recessive genes. The broad heritability of leaf angle trait in waxy corn is relative low （68.5%）, but its narrow heritability is relatively high （72.62%）. In the breeding practices, the early-generation selection is more suitable for the leaf angel trait.

Computationally Efficient MUSIC-Based Algorithm for Joint Direction of Arrival (DOA) and Doppler Frequency Estimation in Monostatic MIMO Radar

The problem of joint direction of arrival (DOA) and Doppler frequency estimation in monostatic multiple-input multiple-output (MIMO) radar is studied and a computationally efficient multiple signal classification (CE-MUSIC) algorithm is proposed.Conventional MUSIC algorithm for joint DOA and Doppler frequency estimation requires a large computational cost due to the two dimensional (2D) spectral peak searching.Aiming at this shortcoming,the proposed CE-MUSIC algorithm firstly uses a reduced-dimension transformation to reduce the subspace dimension and then obtains the estimates of DOA and Doppler frequency with only one-dimensional (1D) search.The proposed CE-MUSIC algorithm has much lower computational complexity and very close estimation performance when compared to conventional 2D-MUSIC algorithm.Furthermore,it outperforms estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm.Meanwhile,the mean squared error (MSE) and Cramer-Rao bound (CRB) of joint DOA and Doppler frequency estimation are derived.Detailed simulation results illustrate the validity and improvement of the proposed algorithm.