Predicting surface quality of γ-TiAl produced by additive manufacturing process using response surface method

Abdulrahman Al-Ahmari,Mohammad Ashfaq,Abdullah Alfaify,Basem Abdo,Abdulrahman Alomar,Abdelnaser Dawud 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.1

Electron beam melting (EBM) has been found to be a promising technology for producing complex shaped parts from gamma titaniumaluminide alloys (γ-TiAl). The parts produced by this process are projected to have dimensions very close to the desired final shapes. However, the surface roughness of the parts produced by EBM is excessively rough. In many applications, it is necessary to improve thequality of manufactured parts using a convenient post process. This paper determines process parameters of end milling when it is usedas a post process for the parts produced by EBM. Design of experiments has been used to study the effect of the selected input parametersof end milling (spindle speed, feed rate, depth of cut and coolant type) on the surface roughness of γ-TiAl parts. Response surface methodologyis used to develop a predictive model for surface roughness. Effects of the selected milling process are investigated. This paperalso optimizes the selected process parameters to minimize the value of the obtained surface roughness.

Genetic and clinical characteristics of pediatric patients with familial hemophagocytic lymphohistiocytosis

Ali Al Ahmari,Osama Alsmadi,Atia Sheereen,Tanziel Elamin,Amal Jabr,Lina El-Baik,Safa Alhissi,Bandar Al Saud,Moheeb Al-Awwami,Ibrahim Al Fawaz,Mouhab Ayas,Khawar Siddiqui,Abbas Hawwari 대한혈액학회 2021 Blood Research Vol.56 No.2

Background Our study was designed to investigate the frequencies and distributions of familial hemophagocytic lymphohistiocytosis (FHL) associated genes in Saudi patients. Methods FHL associated gene screening was performed on 87 Saudi patients who were diagnosed with hemophagocytic lymphohistiocytosis (HLH) between 1995 and 2014. The clinical and biochemical profiles were also retrospectively captured and analyzed. Results Homozygous mutations and mono-allelic variants were identified in 66 (75.9%) and 3 (3.5%) of the study participants, respectively. STXBP2 was the most frequently mutated gene (36% of patients) and mutations in STXBP2 and STX11 accounted for 58% of all FHL cases and demonstrated a specific geographical pattern. Patients in the FHL group presented at a significantly younger age than those belonging to the unknown-genetics group (median, 3.9 vs. 9.4 mo; P=0.005). The presenting clinical features were similar among the various genetic groups and the 5-year overall survival (OS) was 55.4% with a 5.6 year median follow-up. Patients with PRF1 mutations had a significantly poorer 5-year OS (21.4%, P =0.008) and patients undergoing hematopoietic stem cell transplant (72.4%) had a significantly better 5-year OS (66.5% vs. 0%, P =0.001). Conclusion Our study revealed the predominance of the STXBP2 mutations in Saudi patients with FHL. A genetic diagnosis was possible in 80% of the cohort and our data showed improved survival in FHL patients who underwent hematopoietic stem cell transplant.

Intersession Repeatability of Acoustic Rhinometry Measurements in Healthy Volunteers

Mohammed Dhafer Al Ahmari,Jadwiga Anna Wedzicha,John Robert Hurst 대한이비인후과학회 2012 Clinical and Experimental Otorhinolaryngology Vol.5 No.3

Objectives. Acoustic rhinometry is a rapid, reliable and non-invasive technique for the evaluation of conditions associated with impaired nasal patency. This study aimed to examine the intersession repeatability of acoustic rhinometry measurements of unilateral and combined nasal parameters in a group of healthy volunteers. Methods. Twenty healthy volunteers were studied. In each subject, acoustic rhinometry measurements were performed on five consecutive days, with multiple recordings. Five clinically relevant parameters were measured in each session and the intersession repeatability of these measurements was expressed in terms of mean coefficient of variation, intraclass correlation coefficient and inter-item correlations. Results. Intraclass correlation coefficients showed a high, and greater repeatability over time for all the combined (mean)values compared to the unilateral values. All intraclass correlations for combined values were ≥0.80 confirming almost perfect agreement. All intraclass correlations and inter-item correlations were associated with P<0.001. The mean coefficient of variation was low (<10%) for all but the proximal minimum cross sectional area (MCA1) measurements. Conclusion. Acoustic rhinometry provides highly repeatable measurements of nasal patency, which is best for combined (mean) nasal parameters. This property makes it suitable for use in the diagnosis and follow-up of conditions associated with nasal obstruction, either structural or functional. Objectives. Acoustic rhinometry is a rapid, reliable and non-invasive technique for the evaluation of conditions associated with impaired nasal patency. This study aimed to examine the intersession repeatability of acoustic rhinometry measurements of unilateral and combined nasal parameters in a group of healthy volunteers. Methods. Twenty healthy volunteers were studied. In each subject, acoustic rhinometry measurements were performed on five consecutive days, with multiple recordings. Five clinically relevant parameters were measured in each session and the intersession repeatability of these measurements was expressed in terms of mean coefficient of variation, intraclass correlation coefficient and inter-item correlations. Results. Intraclass correlation coefficients showed a high, and greater repeatability over time for all the combined (mean)values compared to the unilateral values. All intraclass correlations for combined values were ≥0.80 confirming almost perfect agreement. All intraclass correlations and inter-item correlations were associated with P<0.001. The mean coefficient of variation was low (<10%) for all but the proximal minimum cross sectional area (MCA1) measurements. Conclusion. Acoustic rhinometry provides highly repeatable measurements of nasal patency, which is best for combined (mean) nasal parameters. This property makes it suitable for use in the diagnosis and follow-up of conditions associated with nasal obstruction, either structural or functional.

Dynamic Output Feedback Robust MPC for LPV Systems Subject to Input Saturation and Bounded Disturbance

Xubin Ping,Zhiwu Li,Abdulrahman Al-Ahmari 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.3

For linear parameter varying (LPV) systems with unknown scheduling parameters and bounded disturbance,a synthesis approach of dynamic output feedback robust model predictive control (OFRMPC) with inputsaturation is investigated. By pre-specifying partial controller parameters, a main optimization problem is solvedby convex optimization to reduce the on-line computational burden. The main optimization problem guarantees thatthe estimated state and estimation error converge within the corresponding invariant sets such that recursive feasibilityand robust stability are guaranteed. The consideration of input saturation in the main optimization problemimproves the control performance. Two numerical examples are given to illustrate the effectiveness of the approach.

Filtering and Intrusion Detection Approach for Secured Reconfigurable Mobile Systems

Rim Idriss,Adlen Loukil,Mohamed Khalgui,Zhiwu Li,Abdulrahman Al-Ahmari 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

This paper deals with reconfigurable secured mobile systems where the reconfigurability has the potential of providing a required adaptability to change the system requirements. The reconfiguration scenario is presented as a run-time automatic operation which allows security mechanisms and the addition-removal-update of software tasks. In particular, there is a definite requirement for filtering and intrusion detection mechanisms that will use fewer resources and also that will improve the security on the secured mobile devices. Filtering methods are used to control incoming traffic and messages, whereas, detection methods are used to detect malware events. Nevertheless, when different reconfiguration scenarios are applied at run-time, new security threats will be emerged against those systems which need to support multiple security objectives: Confidentiality, integrity and availability. We propose in this paper a new approach that efficiently detects threats after reconfigurable scenarios and which is based on filtering and intrusion detection methods. The paper’s contribution is applied to Android where the evaluation results demonstrate the effectiveness of the proposed middleware in order to detect the malicious events on reconfigurable secured mobile systems and the feasibility of running and executing such a system with the proposed solutions.

Effect of Multi-Temperature Aging on Characterization of Aluminum Based Castings Heat Treated Using Fluidized Bed Technique

Kh. A. Ragab,A. M. Samuel,A. M. A. Al-Ahmari,F. H. Samuel,H. W. Doty 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.4

The current study investigates the influences of the fluidized bed heat treatment on the quality indices and microstructural characterization of A356.2 and B319.2 castings. Traditional heat treatment technology,employing circulating air convection furnaces (CF), was used to establish a relevant comparison with fluidized sand bed (FB) for the heat treatment of the alloys investigated, employing T6 continuous aging cycles or multi-temperature aging cycles. The results of alloys subjected to multi-temperature aging cycles reveal that the strength results obtained after the T6 continuous aging treatment of A356 alloys are not improved by means of multi-temperature aging cycles, indicating therefore that the optimum properties are obtained using a T6 aging treatment. The optimum strength properties of B319.2 alloys, however, is obtained by applying multi-temperature aging cycles such as, for example, 230 °C/2 h followed by 180 °C/8 h, rather than T6 aging treatment. In the case of multi-temperature aging cycles, the modification factor has the most significant role in improving the quality index values of 356 and 319 alloys. The FB heattreated alloys have the highest strength values for all heat treatment cycles compared to CF heat-treated alloys; however, the FB has no significant effect on the quality values of 319 alloys compared to the CF.

Filtering and Intrusion Detection Approach for Secured Reconfigurable Mobile Systems

Idriss, Rim,Loukil, Adlen,Khalgui, Mohamed,Li, Zhiwu,Al-Ahmari, Abdulrahman The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

This paper deals with reconfigurable secured mobile systems where the reconfigurability has the potential of providing a required adaptability to change the system requirements. The reconfiguration scenario is presented as a run-time automatic operation which allows security mechanisms and the addition-removal-update of software tasks. In particular, there is a definite requirement for filtering and intrusion detection mechanisms that will use fewer resources and also that will improve the security on the secured mobile devices. Filtering methods are used to control incoming traffic and messages, whereas, detection methods are used to detect malware events. Nevertheless, when different reconfiguration scenarios are applied at run-time, new security threats will be emerged against those systems which need to support multiple security objectives: Confidentiality, integrity and availability. We propose in this paper a new approach that efficiently detects threats after reconfigurable scenarios and which is based on filtering and intrusion detection methods. The paper's contribution is applied to Android where the evaluation results demonstrate the effectiveness of the proposed middleware in order to detect the malicious events on reconfigurable secured mobile systems and the feasibility of running and executing such a system with the proposed solutions.