Optimal Trajectories for Propellant-Free Rendezvous Missions

The paper provides a new approach to utilizing space environmental forces in time- and energy-optimal, propellant-less spacecraft rendezvous missions. Considering the nonlinear form of the relative dynamic equations, rendezvous missions are posed as optimal control problems subject to input saturation. We conduct a direct optimal control approach to obtain optimal trajectories and control inputs. Initially, we consider the differential drag only and conduct a comprehensive analysis of the effect of altitude on the required control input and achieved cost function. Lorentz forces are then utilized with the differential drag, reducing the time required for time-optimal missions. For energy-optimal missions with combined differential drag and Lorentz forces, a weighting matrix in the cost function is introduced to adjust the relative contributions of these forces

THE IMPACT OF A NUMBER OF CHOICES IN A TEST ON THE DIFFICULTY INDICATORS AND DISCRIMINATION

This study aimed to investigate the relationship between a number of choices (alternatives) in a test, and the difficulty indicators and discrimination. A test of multiple choices on statistics students at the University of Jordan was used in this study. The test consisted of 30 items, and three forms (models). Also, a sample of 350 students was studied. The Statistical Package for Social Sciences (SPSS) software and Bilog-Mg were used for the analysis of the data based on the Two parameter models. Therefore, the findings of the present study uncovered a negative association between the number of choices and the difficulty indicator and discrimination

A Control Approach for Nonlinear Stochastic State Uncertain Systems with Probabilistic Safety Guarantees

This paper presents an algorithm to apply nonlinear control design approaches in the case of stochastic systems with partial state observation. Deterministic nonlinear control approaches are formulated under the assumption of full state access and, often, relative degree one. We propose a control design approach that first generates a control policy for nonlinear deterministic models with full state observation. The resulting control policy is then used to build an importance-like probability distribution over the space of control sequences which are to be evaluated for the true stochastic and state-uncertain dynamics. This distribution serves in the sampling step within a random search control optimization procedure, to focus the exploration effort on certain regions of the control space. The sampled control sequences are assigned costs determined by a prescribed finite-horizon performance and safety measure, which is based on the stochastic dynamics. This sampling algorithm is parallelizable and shown to have computational complexity indifferent to the state dimension, and to be able to guarantee safety over the prescribed prediction horizon. A numerical simulation is provided to test the applicability and effectiveness of the presented approach and compare it to a certainty equivalence controller

THE IMPACT OF A NUMBER OF CHOICES IN A TEST ON THE DIFFICULTY INDICATORS AND DISCRIMINATION

This study aimed to investigate the relationship between a number of choices (alternatives) in a test, and the difficulty indicators and discrimination. A test of multiple choices on statistics students at the University of Jordan was used in this study. The test consisted of 30 items, and three forms (models). Also, a sample of 350 students was studied. The Statistical Package for Social Sciences (SPSS) software and Bilog-Mg were used for the analysis of the data based on the Two parameter models. Therefore, the findings of the present study uncovered a negative association between the number of choices and the difficulty indicator and discrimination

The Safety and Efficacy of Cervical Laminectomy and Fusion versus Cervical Laminoplasty Surgery in Degenerative Cervical Myelopathy: A Prospective Randomized Trial

BACKGROUND: There is a lack of evidence of whether degenerative cervical myelopathy (DCM) is best treated through cervical laminoplasty (CLP) or cervical laminectomy with lateral mass fusion due to the lack of prospective randomized studies that are well designed. We conducted the largest prospective randomized trial to date to determine the comparative effectiveness and safety of both approaches. METHODS: In this prospective, randomized trial, we randomly assigned patients who had symptoms or signs of DCM to undergo either cervical laminectomy and lateral mass fixation (CLF) or CLP. The primary outcome measures were the change in the Visual Analog Scale (VAS), neck disability index, modified Japanese Orthopedic Association (mJOA) score, and Nurick’s myelopathy grading 1 year after surgery. The secondary outcome measures were the intraoperative, post-operative complications, hospital stay, C2-7 Cobb’s angle, and Odom’s criteria. The follow-up period was at least 1 year. RESULTS: A total of 30 patients (mean age, 54.5 ± 5.5 years, 70% of men) underwent prospective randomization. There was a significantly greater improvement in neck pain (VAS) in the CLF group at 1 year (p < 0.05). The improvement in the mJOA and Nurick’s myelopathy grading showed insignificant improvement between both groups. Furthermore, there was no significant difference in the patient’s post-operative satisfaction (Odom’s criteria). The mean operative time was significantly longer in the CLF group (p < 0.001), with no significant difference in the post-operative complications, however, there was a higher rate of C5 palsy, dural tear and infection in the CLF, and a higher rate of instrumentation failure in the CLP. The mean hospital stay was significantly longer in the posterior group (p < 0.05). Finally, there was a significant better improvement in the C2-7 Cobb’s angle at 1 year in the CLF group (p < 0.05). CONCLUSION: Among patients with multilevel DCM, the CLF approach was significantly better regarding the post-operative pain and Cobb’s angle while the CLP was significantly better in terms of shorter hospital stay and operative time

The phytochemical and biological investigation of Jatropha pelargoniifolia root native to the Kingdom of Saudi Arabia

Extensive phytochemical analysis of different root fractions of Jatropha pelargoniifolia Courb. (Euphorbiaceae) has resulted in the isolation and identification of 22 secondary metabolites. 6-hydroxy-8-methoxycoumarin-7-O-β-d-glycopyranoside (15) and 2-hydroxymethyl N-methyltryptamine (18) were isolated and identified as new compounds along with the known diterpenoid (1, 3, 4, and 7), triterpenoid (2 and 6), flavonoid (5, 11, 13, 14, and 16), coumarinolignan (8–10), coumarin (15), pyrimidine (12), indole (17, 18), and tyramine-derived molecules (19–22). The anti-inflammatory, analgesic, and antipyretic activities were evaluated for fifteen of the adequately available isolated compounds (1–6, 8–11, 13, 14, 16, 21, and 22). Seven (4, 6, 10, 5, 13, 16, and 22) of the tested compounds showed a significant analgesic effect ranging from 40% to 80% at 10 mg/kg in two in vivo models. Compound 1 could also prove its analgesic property (67.21%) when it was evaluated on a third in vivo model at the same dose. The in vitro anti-inflammatory activity was also recorded where all compounds showed the ability to scavenge nitric oxide (NO) radical in a dose-dependent manner. However, eight compounds (1, 4, 5, 6, 10, 13, 16, and 22) out of the fifteen tested compounds exhibited considerable in vivo anti-inflammatory activity which reached 64.91% for compound 10 at a dose of 10 mg/kg. Moreover, the tested compounds exhibited an antipyretic effect in a yeast-induced hyperthermia in mice. The activity was found to be highly pronounced with compounds 1, 5, 6, 10, 13, and 16 which decreased the rectal temperature to about 37 °C after 2 h of the induced hyperthermia (~39 °C) at a dose of 10 mg/kg. This study could provide scientific evidence for the traditional use of J. pelargoniifolia as an anti-inflammatory, analgesic, and antipyretic

The effects of circuit exercise training strategy on health-related physical fitness level and biomarkers in elderly people with cardiovascular diseases

This study investigated the effects of a 12-week circuit exercise training intervention on health-related physical fitness and biomarkers in elderly adults with cardiovascular diseases. A total of 69 participants underwent the circuit exercise training program, which included stretching, aerobic activity, and weight training. The results showed that the participants had improved performance in cardiovascular and strength tests, with grip and back muscle strength showing improvement. However, sit-ups were lower than the average, and power, reaction time, and agility needed more effort. The high sensitivity C-reactive protein value reached a medium infection risk level for cardiovascular illnesses. The study concluded that there was a strong association between health-related physical fitness and biomarker index in senior persons with a medium risk cluster of cardiovascular illnesses. The study also found that BMI correlated positively with biomarker index, while cardiovascular fitness, agility, and flexibility correlated negatively with biomarker index

Monte Carlo Grid Dynamic Programming: Almost Sure Convergence and Probability Constraints

Dynamic Programming (DP) suffers from the well-known ``curse of dimensionality'', further exacerbated by the need to compute expectations over process noise in stochastic models. This paper presents a Monte Carlo-based sampling approach for the state space and an interpolation procedure for the resulting value function, dependent on the process noise density, in a "self-approximating" fashion, eliminating the need for ordering or set-membership tests. We provide proof of almost sure convergence for the value iteration (and consequently, policy iteration) procedure. The proposed meshless sampling and interpolation algorithm alleviates the burden of gridding the state space, traditionally required in DP, and avoids constructing a piecewise constant value function over a grid. Moreover, we demonstrate that the proposed interpolation procedure is well-suited for handling probabilistic constraints by sampling both infeasible and feasible regions. While the curse of dimensionality cannot be entirely avoided, this approach offers a practical framework for addressing lower-order stochastic nonlinear systems with probabilistic constraints, where traditional DP methods may be intractable or inefficient. Numerical examples are presented to illustrate the convergence and convenience of the proposed algorithms.Comment: 6 pages, 1 figur

Effect pH on Structural and Optical Properties of Nanostructure CdS Films Prepared by Chemical Bath Deposition Technique

Nanostructures CdS films were prepared by chemical bath deposition technique on glass substrates, where the cadmium nitrate salt was used as a source of cadmium ions and thiourea (SC(NH2)2) as a source of sulphide ions(S-2). The deposition were carried out at different pH values. Structure of these films was characterized by X-ray diffraction and atomic force microscope (AFM). CdS films deposited have cubic(zinc blende) structure and the grain size of nanoclusters decreases with increasing pH value in solution. The optical properties study by transmission spectra and the films have highly transmittance in visible region of spectrum and reach to more than 86%. The CdS films have band gap increase from 2.42 to 2.58 eV with increasing pH value in solution