This study aims to identify and predict objects underwater using the autoregressive moving average with exogenous excitation (ARMX) model in such a way that the outcome of the model is similar to actual measurements. It is used for parameter estimation. This model is validated by comparing results in actual model with ARMX model, autoregressive with an exogenous variables, and Box Jenkins (BJ) model. The results are analyzed in frequency and time domain by using mean square error criterion. Initial results show that ARMX predicts the acoustic scattering response with an accuracy of 96%, while ARX provides an accuracy of 78%, and BJ model poorly estimates the signal with an accuracy of 35%. ARMX also provides higher accuracy of detection by 7-8% as compared to the existing techniques.

Diabetic Retinopathy (DR) is one of the major eye diseases that causes damage to retina of the human eye ball due to the rupture of tiny blood vessels. DR is identified by the ophthalmologists on the basis of various specifications i.e., textures, blood vessels and pathologies. The ophthalmologists are recently considering software for eye diseases detection based on image processing designed by the computing techniques and bio-medical images. In the analysis of medical imaging, traditional techniques of image processing and computer vision have played an important role in the field of ophthalmology. From the past two decades, there is a tremendous advancement in the development of computerized system for DR detection. This paper comprises the five parts of analysis on image based retinal detection DR, named as review of low varying contrast techniques of the retinal fundus Images (RFI), review of noise effect in the fundus images, review of pathology detection method from the retinal fundus images, review of blood vessels extraction from the RFI, and review of automatic algorithm for the DR detection. This paper presents a comprehensive detail to each problem in the retinal images. The procedures that are currently utilized to analyze the contrast issue and noise issues are discussed in detail. The paper also explains the techniques used for segmentation. In the end, the recent automated detection system of related eye diseases or DR is described.

Location-based services (LBS) are the services that are used through users’ mobile devices and provide them the information regarding nearby restaurants, hospitals, gas stations, shopping malls, cinema (to name a few). While using LBS, a user needs to provide his/her location coordinates (geo-coordinates) to the LBS server. The revelation of a user’s location may seriously jeopardize his/her privacy. A common solution to this problem is the use of an intermediate anonymizer server that obfuscate the real location of a user among k other users. However, in this scenario, the anonymizer server must be a trusted and therefore, inherits the trust related issue and may also become a single point of failure. Moreover, if anonymizer compromises then the privacy of all the users is compromised. A vehicular adhoc network (VSN) is a subset of a mobile adhoc network (MANET) with some unique characteristics such as rapid speed of nodes (vehicles) that quickly change topologies. A vehicular social network is a combination of VANET and online social network. A VSN is formed by likeminded drivers/passengers or by common location. Like mobile nodes, the vehicles also utilize LBS services. However, an anonymizer cannot be used in this scenario because it needs to be updated with current locations of vehicles and therefore, jeopardizes the privacy of vehicles. A VSN can significantly help in this scenario. This research proposes a distributed k-anonymity based scheme that considers the social ties between the users of VSN and enable vehicles to use LBS in a privacy preserving manner. The proposed scheme uses a trusted authority (TA) such as a government law enforcement agency, that registers vehicles. However, the TA does not know what services are requested by a vehicle. On the other hand, the LBS server does not know which vehicle is requesting the service. In the end, the computational and communication overhead of the scheme is presented. The low computational overhead of TA, LBS server and vehicles shows that LBS can serve several vehicles in a very short time. Similarly, the TA can register and provide pseudo-identities to a number of vehicles without any significant delays.

Seismic excitations and other lateral dynamic distress cause the structure’s foundation to interact with the superstructure’s response. Consequently, the surplus stress distribution takes place. This disturbance in the lateral stiffness of the system can cause un-satisfaction with the adopted code provisions. In the above scenario, soil structure interaction of the Moment Resisting Frames (MRFs) becomes very crucial. This article deals with soil stiffness on the long-span MRFs designed with two modern building codes, namely Saudi Building Code (based on American Standards) and Eurocodes. High and medium ductility with parameter and spatial frame configurations are considered in this study. Each frame is analysed considering the foundation stiffness, calculated based on FEMA recommendations. Hence, a total of 18 cases are examined, conducting a modal response spectrum analysis. The period, top displacements, reactions, and damageability criterion for the analyzed frames are compared. It is shown that the consideration of SSI (Soil Structure Interaction) is paramount for frames with such spans, especially when subjected to high seismic forces.

Distributed Generation (DG) allocation in distribution network is an optimal choice in maximizing benefits and reducing power losses. In this paper, self-adaptive differential evolution (SaDE), an optimization approach, is used for optimal site and capacity of DG. Different types of DGs such as solar PV and wind turbine (WT) at constant and near unity power factor are integrated into the distribution system. For validation of the proposed algorithm, IEEE 33-bus, 69-bus and 119-bus radial distribution networks are considered. The results show that the proposed algorithm has the ability to find global minimum value of objective function along with the appropriate site and capacity of solar PV and WT type DG. Moreover, the results of proposed method are compared with other existing techniques in order to show its effectiveness. The comparison shows that the proposed technique has the ability to get the lowest power losses with the smallest DG size. Thus, the proposed technique has the ability to find an optimal decision vector that makes it suitable for real-time applications.

Arsenic (As) being a carcinogenic element present in drinking water in the less developed areas in the deprived countries contributes to many infectious diseases. The removal of arsenic traces from water needs to have an easy and efficient way for poor countries. Concerning this, a low-cost bio-adsorbent from Rice husk is prepared to remove arsenic from groundwater. Preparation of the absorbent is performed by crushing, sieving, washing and drying the rice husk. The Arsenic present in groundwater samples before and after treatment were tested by Arsenic kit. Batch experiments were carried out with ten contaminated samples of groundwater from Indus river origin area (Nasarpur) to investigate the influence of operating parameters such as adsorbent bed height (ABH) and initial arsenic concentration and residence time(TR) on As removal efficiency using locally fabricated adsorption column. Environmental parameters such as pH, temperature, TDS, and EC were also determined. It was observed that the highest optimized removal efficiency of 90% was achieved at ABH 30 cm: residence time, 60 minutes for feed arsenic concentration of 80 ppb samples. These results suggest that this bio-adsorbent can provide an easy, efficient, and economical method for removing As ions from effluents and water resources.

The environmental problems caused by industrial pollutants and global warming are on the rise. There is a need to develop a technology for reducing harmful pollutants. The co-combustion is getting serious attention by the scientists regarding its key facets to reduce the environmental pollutants. Its function is based on utilization of biomass with coal. In this work different types of biomass were used with coal samples to identify the suitable methodology. The biomass resource fulfills the requirement with reducing environmental pollutants and overcome energy crises. The ratios of biomass with coal samples were analyzed using stack gas analyzer. The banana tree waste (BTW) was found to be effective for reducing CO2 and CO emission. While, Cow dung manure (CDM) was found to be efficacious to decrease NOx. LC 80%+BTW 20% for SO2 and CDM for NO. To conclude, CDM and BTW decreases the emissions keeping blending ratio 80:20 with lignite coal to biomass in co-combustion respectively.

Concrete is the most important and most consumed construction material in global construction industry. The properties of concrete are greatly influenced by properties of its constituents and curing methods utilized for preparation of specimens. This study is focused on investigating the influence of three common curing methods, i.e., ponding, sprinkling and wet cover curing on compressive strength behavior of concrete. In total, 45 cubes were casted and tested after curing for 3, 7, 14, 28 and 56 days. The obtained results suggest that ponding method of concrete curing is most effective among all the three methods of concrete curing considered in this study. After ponding, the performance of concrete cured with wet cover curing method was quite acceptable. Moreover, the study also suggested that sprinkling method of curing gives lowest compressive strength due to greater moisture movement which abates the hydration of binder in concrete. This study will be helpful for construction practitioners in deciding the best-suited curing method under given conditions and available methods of preparation of concrete.

Concrete is the most used building and construction material globally due to the ease of availability and durability. It is a well-known fact that concrete can easily withstand compressive stresses; however, it fails under tension. To improve this deficiency, steel bar reinforcement has been used. However, with the steel reinforcement, additional permanent self-weight is transferred on the structure and is prone to corrosion. Hence, engineers and researchers have been working to search for more sustainable reinforcing material that could be cost-effective and simultaneously increase tensile strength. This experimental work was carried out to study the influence of long (38.1 mm) polypropylene (PP) fibres on the workability and mechanical strengths (compressive and flexural) of concrete. Three different fibre fraction content, 0.20%, 0.25% and 0.30% were selected to reinforce concrete. A total of 12 cylinders of 300mm×150mm dimension (3 cylinders per mix) and 12 beams of 609.6mm×304.8mm×101.6mm dimension (3 beams per mix) were used to determine the compressive strength and flexural strength after the samples achieved 28 days curing. Based on the results, it can be observed that longer fibres do not significantly influence the compressive strength as much as they do on flexural strength. Furthermore, longer length fibres, like shorter fibres, obstruct the workability of concrete. Comparing with previous findings, it can be concluded that for patching of macrocracks, longer length PP fibres should be used.

A systematic study was carried out to improve the mechanical properties of medium carbon steel grade SAE 1040 by heat treatment processes. Test specimen were prepared according to ASTM standards. Test specimen were heat treated in Gas furnace at austenitization temperature of 700C to obtain fully austenite structure, soaked for 90 minutes, cooled in air and furnace, and quenched in water separately. Mechanical properties such as hardness, tensile strength, yield strength, breaking strength, Young’s Modulus, elongation and impact energy were investigated in this study. It was observed that water quenching enhances materials’ hardness, tensile strength, yield strength, breaking strength and Young’s Modulus while reducing the elongation and impact energy as compared with untreated specimen. Furnace cooling decreases materials’ hardness, tensile strength, yield strength, breaking strength, Young’s Modulus while increasing the elongation and impact energy as compared with untreated specimen. Air cooling improved the materials’ mechanical properties such as hardness, tensile strength, yield strength, breaking strength, Young’s Modulus, elongation and impact energy as compared with untreated specimen. The results of this study show that the heat treatment technique greatly influences the mechanical properties of medium carbon steel grade SAE 1040.

The disposal of solid waste in open environment is a serious alarming concern that needs immediate attention from the researchers. The hazardous solid agro-industrial wastes which include: wheat straw ash, rice husk ash, corn cob ash and sugarcane bagasse ash (SCBA), having pozzolanic properties, have a versatile use in concrete. The solid pozzolana enhances the various concrete properties by the reaction of silicates with calcium hydroxide in the presence of water, which in result generate a saturated zone of calcium silicate hydrate (CSH) gel. This C-S-H gel reduces the amount of calcium hydroxide C(OH)2 during the hydration process of cement. Very limited research works have been done on concrete by partially replacing cement with SCBA. This research work was focused on evaluating the properties of concrete by partially replacing cement with SCBA at 0, 5, 10, and 15 percentages. Compressive strength, Strength activity index, and water absorption of all mixes were examined. And it was observed that all SCBA mixes showed an increase in compressive strength and at 10% replacement the strength activity index was at a peak of 115.67%, but all the SCBA mixes showed a strength activity index greater than 75% which satisfied the standard specification. The water absorption test for all SCBA mixes showed a slight increase in water absorption.

In this study, the quality of groundwater used for drinking purposes at Rajanpur Tehsil Pakistan is investigated. Water contamination causes several health problems to human being and the severity of problems mainly depends upon the level of pollutants present in water. Physical, chemical, and biological parameters of groundwater for twelve locations are analyzed using standard procedures. The obtained results are compared with the standards set by WHO. Most of the chemical parameters are found within the WHO standards except Arsenic, Calcium, and Sulfate at various locations. The Arsenic is found beyond WHO standards at nine locations with an increased percentage of 400% at three locations namely village Mehre Wala, Sehnwal, Near Basti Bhayan, and is also found beyond the permissible limit, i.e., upto 150% at six locations Sikhaniwala, Kot Mithan, Basti Nazru, Basti Asni, Jalal Pur, and Qutab Pul. Only three locations show satisfactory results, namely village shikarpur, village Murghai and Basti Lakha. The percentage of calcium at five locations such as Murghai, Basti Nazru, Basti Asni, Basti Lakha, and Chak Jalal Pur (Pull Pathan) is found to be 44%, 12%, 17.33%, 76%, and 49.33%, which is much higher than the WHO standards. Meanwhile, the Sulphate is also found to be beyond WHO standards at four locations, i.e. 30.8% for Mehrewala, 37.6% for Murghai, 34.8% for Basti Lakha and 34% for Chak Jalal Pur (Pull Pathan). Biological contamination including total coliform and fecal coliform are found to be beyond the limit at Sehanwala, Rangpur, Shikarpur, and Basti Nazru locations. The higher percentage of Arsenic, calcium, and sulfate in water indicate that the groundwater is not suitable for drinking purpose. Sustainable water treatment is highly recommended for drinking water at the identified contaminated location.

Two grades of bitumen, (60/70 and 80/100), were modified by addition of Local Crumb Rubber (LCR) by weight of base bitumen. To investigate the effects of short-term aging on modified and LCR modified bitumen, Rolling Thin Film Oven (RTFO) test was used to simulate the short term aging. Dynamic shear rheometer (DSR) was used to assess the rheological properties of bitumen, both before and after aging. It was observed that at 65 degree Celcius on aging, the phase angle (sigma) of unmodified bitumen decreased by 3 and 4% for 60/70 and 80/100 bitumen respectively; whereas, for 60/70 LCR modified bitumen, the phase angle (sigma) on RTFO aging decreased by 7% for all LCR content (10, 15 and 20%) by weight of base bitumen. However, on RTFO aging (sigma), values for LCR modified 80/100 bitumen varied across different LCR content and could not be generalized. The complex modulus |G*| of LCR modified 60/70 bitumen increased on aging for both modified and unmodified bitumen at 65C, but with the increase in LCR content, the difference between bitumen aged and un-aged values of |G*| was considerably lowered. An interesting finding was for 80/100 bitumen modified with 20% LCR content by weight, which showed a reduction in |G*| values and an increase in (sigma) values on aging. This shows that to some extent, LCR compensates for the stiffening effects of aging.

There is a growing need of construction around the globe. This need tends to provide newer opportunities for construction of buildings over reclaimed lands or earth filled areas. Mostly, the earth is filled with soils as it is an easily available material. Soil is a complex materials, and its properties can vary due to several reasons. If not understood properly, it can damage undisturbed samples collected from earth-filled soils. The basic properties of soils, the stress-strain behavior and strength parameters are presented and discussed. Results show that soil exhibits strain hardening and normally consolidated behavior in direct shear and oedometer test respectively. It is observed that the compression index values are in the range of 0.157 to 0.182 which indicates that the material is silty soils with low plasticity. The allowable bearing capacity in our study was 305 kPa and allowable load on footing was 987 kN. The strength parameters, i.e., friction angle and cohesion are 37 degree and 2 kPa respectively.

Chromium being a carcinogenic element present in drinking water in the less developed areas in the poor countries contributes to many infectious diseases. The removal of chromium traces from water needs to have an easy and efficient way for poor countries. Concerning this, a low-cost industrial bio-adsorbent based on bagasse (the sugar industry waste) is prepared and characterized for Cr (VI) removal from aqueous solutions. Preparation of the absorbent is performed by carbonization and steam activation of sugarcane bagasse (SCB). The FTIR spectra and the morphology of the adsorbent before and after Cr (VI) removal was studied using FTIR and SEM. All the experiments were carried out in a batch process with laboratory-prepared samples to study the effects of pH, adsorbent dose, adsorbate concentration, shaking time and shaking speed. It was observed that the highest removal efficiency was achieved at pH=2, adsorbent dose=0.75 g, adsorbate concentration=60 mg/L, shaking speed=150 rpm, and shaking time=20 minutes. These results suggest that this bio-adsorbent can provide a simple, effective, and cheap method for removing Cr (VI) ions from effluents and water resources.

The worldwide increasing amount of municipal solid waste causes a major problem in managing waste as well as requires an effective solution to manage the waste generation. In Malaysia, landfilling is the main alternative technique for managing solid waste. In the same way, the main advantage of having a landfill is that it is easy to operate and comparatively lower in cost. Thus, in Malaysia, total 296 municipal solid waste landfills are open to overcome this issue. Drawbacks of landfilling can includes; i) generation of noxious gases, ii) leachate wastewater contamination of both ground and surface water, iii) problems such as odor, noise, and dust, iv) attraction of disease vectors and, v) the requirement for considerable land area. This present research study focuses on the characterization of Simpang Renggam Landfill (SRLS) Site such as its organic constitutes (mg/L), Ammoniacal Nitrogen (mg/L), SS (mg/L), BOD5/COD, BOD5 (mg/L), and pH. All the analyzed results were compared with the past researchers’ researches and also were compared with Malaysian Environmental Quality Act 1974. From the results, it is concluded that the Simpang Renggam Landfill Site was characterized old (stabilized) landfill leachate wastewater with BOD5/COD > 0.1. For the SRL site, it is recommended that physical-chemical method is better fitted for the leachate wastewater treatment and the aerated lagoon technique does not support the treatment of aging leachate.

arithmetic expression grammar and its equivalent LL(1) is used in the study which is converted. A transformation method is defined which converts the selected grammar into a Greibach normal form that is further converted into a GNF based parser through a method proposed in the study. These two parsers are analyzed by considering 399 cases of arithmetic expressions. During statistical analysis, the results are initially examined with the Kolmogorov-Smirnov and Shapiro-Wilk test. The statistical significance of the proposed method is evaluated with the Mann-Whitney U test. The study described that GNF based LL(1) parser for arithmetic take fewer steps than conventional LL(1) grammar. The ranks and asymptotic significance depict that the GNF based LL(1) method is significant than the conventional LL(1) approach. The study adds to the knowledge of parsers itself, parser expression grammars (PEG’s), LL(1) grammars, Greibach Normal Form (GNF) induced grammar structure, and the induction of Arithmetic PEG’s LL(1) to GNF based grammar.

The utilization of (HSC) high strength concrete in the construction industry is increasing all over the world because it reduces the cross-section of structural members and increases floor area. High strength concrete can be produced by using high cement content with low w/c ratio, mineral admixtures, and chemical admixture, and with suitable fiber. Nevertheless, in this research, HSC mix was achieved with the use of a special type BASF Master (M)/Polyheed 996 super-plasticizer based on polycarboxylic ether available in the market which reduced the w/c of concrete mixes, albeit attaining adequate workability. Compressive strength, up to 63 Mpa at 28 days, was achieved at slump value 178 mm by utilizing locally available materials like cement, sand, and coarse aggregates with a maximum 1.2% (by weight of cement) dosage of super-plasticizers. HSC has high workability, and to control the workability, different percentages of polyester fiber length 32 mm were also added to HSC. Polyester fiber controls the workability and improves the properties of HSC. There were four mixes designed with polyester fiber. The addition of polyester fiber content was 0.2%, 0.3%, 0.4%, and 0.5% (by weight of cement) in HSC, and the slump value were 153mm, 127mm, 102mm and 76mm respectively. It was observed that the usage of polyester fiber (0.2% to 0.5%) decreases workability by 14% to 57% of HSC. Therefore, it was concluded that increasing the percentage of fiber decreases the slump to the required value.

This study has been designed to evaluate the impact of gamified recruitment on team effectiveness in the telecom sector of Pakistan. The sample of 120 respondents was designed to collect the data. This includes 30 respondents each from 4 telecom sector organizations of Pakistan. 110 responses returned complete feedback which gave the response rate of 91.66%. The results reveal that there is a positive impact of the gamified recruitment on team effectiveness at the telecom sector of Pakistan. As the model fitness is highly appreciated which is 0.850 at alpha is equals to 0.000 while beta is 92.3%. Similarly, the persuasive, economic, and informative value of gamified recruitment has been tested on virtual teams’ dimension of team effectiveness of the telecom sector of Pakistan. The model fitness was found 73% and the values found to be significant and influencing to accept the hypothesis. Moreover, similar results have also been identified after testing the persuasive, economic, and informative value of the gamified recruitment to the physical and project teams’ effectiveness at the telecom sector of Pakistan.

COVID-19 has become one of the most highly orated subject matter in these days. Countries have taken many viable actions to prevent the spread of the virus directed by international recommendations, which led to many disputes concerning wearing a face mask as a preventive measure against the virus. This study aims to assess and compare the overall accuracy, macro precision, macro F-measure and macro recall of the different decision models towards the COVID-19 mask-wearing practices via sentiment analysis. Tweets are labeled and text pre-processing techniques are applied as stemming, normalization, tokenization, and stop-word removal. Subsequently, the tweets are transformed into master feature vectors by applying various feature extraction, feature representation, feature selection and word embedding techniques with five supervised machine learning decision models to predict maskwearing practices reinforced from Twitter tweets. Moreover, the highest macro F-measure and macro precision are found with feature extraction as hybrid-grams, feature representation as TF-IDF, feature selection as Chi-Squared Test, and highest macro recall with feature extraction as BOW, feature representation as TF-IDF, feature selection as ANOVA F-value. Hence, this study concludes that the Naive Bayes (NB) algorithm outperforms other decision models with master feature vectors applied. In addition, it also outperforms word embedding techniques.

The magnetic tunnel junction based on magnesium oxide is a device consisting of two ferromagnetic layers separated by the insulating layer of magnesium oxide which has proved to be the foundation of contemporary magnetic read sensors in hard disk drives (HDD). This paper sheds light on the usage of Two-Tone Testing method for the complete treatment of the non-linear impact of sensors related to dynamic ones which is not possible with conventional linear as well as one-tone measurement techniques. Two-tone technique is considered novel, but is challenging in the area of magnetic materials and magnetism because of the device’s nature. However, the experimental results demonstrate the usage of “Two-Tone Testing” to characterize the non-linear properties of a magnetic sensor. Addressing non-linear properties of a magnetic sensor helps proper design of magnetic sensors before the production, thereby signifying the importance of this approach.

Arsenic is a carcinogenic element capable to get into water bodies and drinking water supplies from natural deposits and industrial practices. Its presence in drinking underground water is highly toxic to human health. The study is focused on the development of indigenous Iron-Coated Pottery Granules (ICPG) to remove As from groundwater of Hala City. The developed ICPG was agitated with local clay white flour and water. A low-cost adsorbent namely ICPG was synthesized for the expulsion of As from underground water. The ICGP was characterized with SEM and FTIR techniques. Furthermore, the impact of physical parameters including adsorbate concentration, dosage, mixing time, pH, and contact time on As removal efficiency was investigated in batch experiments. The maximum removal efficiency was achieved with an adsorbent dosage of 0.5 grams at pH =7 for a contact time of 90 minutes when agitated at a speed of 150 r/min. The arsenic removal efficiency was found highly dependent on contact time increase and optimum pH (maximum removal achieved at strong adsorption of As at pH 4–7), however, the rise of adsorbate concentration resulted in the decrement in the efficiency after certain range. Batch adsorption study of underground water sample collected from Hala, Sindh, Pakistan was performed with satisfactory results, i.e. 94 arsenic removal from water. All the water samples were analyzed through atomic absorption Spectrophotometer. The investigation has indicated that ICPG is an exceptionally favourable material for As removal from drinking underground water and can be applied to handle the arsenic issue in most of the regions of Sindh province.

This paper proposes an adaptive learning control and monitoring of oxygen for patients with breathing complexities and respiratory diseases. By recording the oxygen saturation levels in real-time, this system uses an adaptive learning controller (ALC) to vary the oxygen delivered to the patient and maintains it in an optimum range. In the presented approach, the PID controller gain is tuned with the learning technique to provide improved response time and a proactive approach to oxygen control for the patient. A case study is performed by monitoring the time varying health vitals across different age groups to gain a better understanding of the relationship between these parameters for COVID-19 patients. This information is then used to improve the standard of care provided to patients and reducing the time to recovery. Results show that ALC controls the oxygen saturation within the target range of 90% to 94% SpO2, 77% and 80.1% of the time in patients of age groups 40-50 years old and 50-60 years old, respectively. It also had faster time to recovery to target SpO2 range when the concentration dropped rapidly or when the patient becomes hypoxic as compared to the manual control of the oxygen saturation by the healthcare staff.

Silica fume is an industrial by-product that can be used as a partial replacement of cement to enhance the strength related properties of roller compacting concrete. In past, industrial wastes were used to dump on earth, river, and sea that creates a hazardous environment for aquatic life as well as for humans. Nowadays, the use of industrial by-products as cement replacement is popular in the construction industry because it protects the environment from hazards. In this research, the effect of silica fume as partial replacement of sulphate resisting cement is investigated on the compressive strength of roller compacting concrete. Total four types of mix proportions were casted using concert mix ratio as 1:2:4 to investigate the compressive strength of roller compacting concrete at 7 and 28 days of curing age. The sulphate resisting cement was partially replaced with silica fume by 0%, 5%, 10%, and 15% by weight of cement. The zero slump was maintained in all mixes. It was observed that the mix proportions containing 5% and 15% silica fume replacement showed maximum and minimum compressive strength of roller compacting concrete respectively.