Effects Of Curing Angle On Laminated Unsaturated Polyster : Epoxy Composites Structures

Small and Medium Industries or Enterprises (SMI/E) in Malaysia that involved in composite industry faced a lot of challenges, ranging from raw materials, processes and product itself. The high production cost was due to the confined production floor as a result of horizontal curing plane for long hours. A solution was proposed by investigating the different curing angles (0˚, 10˚, 20˚, 30˚, 40˚, 50˚, 60˚, 70˚, 80˚ and 90˚) to find out the best curing angle via hand lay-up assisted by vacuum bagging technique at room temperature thus is able to fabricate the composite parts with similar or improved properties besides saving space. A series of four-ply laminated glass fiber composite structures were impregnated with unsaturated polyester and epoxy separately then set to cure at different curing direction. The composite structures were tested with density, tensile, flexural and hardness tests to determine the mechanical performance, and also the SEM images were examined and analysed on fracture samples. Across the samples at different curing angles from curing angles of 0˚ to 90˚, the peak performance found out to be frequently at 40˚. However, the vertically cured 90˚ composite structure found out to have improved mechanical properties (1.089 % to 4.280 %) when benchmarked with horizontal curing plane at 0˚. Curing at a tilting angle is possible to carry out. Therefore, the vertical curing of composite parts can be recommended to SMI/E in view of its improved performance and optimum space management solution

The In-Transit Vigilant Covering Tour Problem of Routing Unmanned Ground Vehicles

The routing of unmanned ground vehicles for the surveillance and protection of key installations is modeled as a new variant of the Covering Tour Problem (CTP). The CTP structure provides both the routing and target sensing components of the installation protection problem. Our variant is called the in-transit Vigilant Covering Tour Problem (VCTP) and considers not only the vertex cover but also the additional edge coverage capability of the unmanned ground vehicle while sensing in-transit between vertices. The VCTP is formulated as a Traveling Salesman Problem (TSP) with a dual set covering structure involving vertices and edges. An empirical study compares the performance of the VCTP against the CTP on test problems modified from standard benchmark TSP problems to apply to the VCTP. The VCTP performed generally better with shorter tour lengths but at higher computational cost

The effect of manganese oxide on the sinterability of hydroxyapatite

The sinterability of manganese oxide (MnO2) doped hydroxyapatite (HA) ranging from 0.05 to 1 wt% was investigated. Green samples were prepared and sintered in air at temperatures ranging from 1000 to 1400 °C. Sintered bodies were characterized to determine the phase stability, grain size, bulk density, hardness, fracture toughness and Young's modulus. XRD analysis revealed that the HA phase stability was not disrupted throughout the sintering regime employed. In general, samples containing less than 0.5 wt% MnO2 and when sintered at lower temperatures exhibited higher mechanical properties than the undoped HA. The study revealed that all the MnO2-doped HA achieved >99% relative density when sintered at 1100–1250 °C as compared to the undoped HA which could only attained highest value of 98.9% at 1150 °C. The addition of 0.05 wt% MnO2 was found to be most beneficial as the samples exhibited the highest hardness of 7.58 GPa and fracture toughness of 1.65 MPam1/2 as compared to 5.72 GPa and 1.22 MPam1/2 for the undoped HA when sintered at 1000 °C. Additionally, it was found that the MnO2-doped samples attained E values above 110 GPa when sintered at temperature as low as 1000 °C if compared to 1050 °C for the undoped HA

Optimal Attack against Cyber-Physical Control Systems with Reactive Attack Mitigation

This paper studies the performance and resilience of a cyber-physical control system (CPCS) with attack detection and reactive attack mitigation. It addresses the problem of deriving an optimal sequence of false data injection attacks that maximizes the state estimation error of the system. The results provide basic understanding about the limit of the attack impact. The design of the optimal attack is based on a Markov decision process (MDP) formulation, which is solved efficiently using the value iteration method. Using the proposed framework, we quantify the effect of false positives and mis-detections on the system performance, which can help the joint design of the attack detection and mitigation. To demonstrate the use of the proposed framework in a real-world CPCS, we consider the voltage control system of power grids, and run extensive simulations using PowerWorld, a high-fidelity power system simulator, to validate our analysis. The results show that by carefully designing the attack sequence using our proposed approach, the attacker can cause a large deviation of the bus voltages from the desired setpoint. Further, the results verify the optimality of the derived attack sequence and show that, to cause maximum impact, the attacker must carefully craft his attack to strike a balance between the attack magnitude and stealthiness, due to the simultaneous presence of attack detection and mitigation

L2L^{2}-Hodge theory on complete almost K\"{a}hler manifold and its application

Let $(X,J,\omega)$ be a complete $2n$-dimensional almost K\"{a}hler manifold. First part of this article, we construct some identities of various Laplacians, generalized Hodge and Serre dualities, a generalized hard Lefschetz duality, and a Lefschetz decomposition, all on the space of $\ker{\Delta_{\partial}}\cap\ker{\Delta_{\bar{\partial}}}$ on pure bidegree. In the second part, as some applications of those identities, we establish some vanishing theorems on the spaces of $L^{2}$-harmonic $(p,q)$-forms on $X$ under some growth assumptions on the K\"{a}her form $\omega$. We also give some $L^{2}$-estimates to sharpen the vanishing theorems in two specific cases. At last of the article, as an application, we study the topology of the compact almost K\"{a}hler manifold with negative sectional curvature.Comment: 30 pages, Submitted. The main theorems remain unchanged. We remove the section about Theorem 1.

Modeling and Detecting False Data Injection Attacks against Railway Traction Power Systems

Modern urban railways extensively use computerized sensing and control technologies to achieve safe, reliable, and well-timed operations. However, the use of these technologies may provide a convenient leverage to cyber-attackers who have bypassed the air gaps and aim at causing safety incidents and service disruptions. In this paper, we study false data injection (FDI) attacks against railways' traction power systems (TPSes). Specifically, we analyze two types of FDI attacks on the train-borne voltage, current, and position sensor measurements - which we call efficiency attack and safety attack -- that (i) maximize the system's total power consumption and (ii) mislead trains' local voltages to exceed given safety-critical thresholds, respectively. To counteract, we develop a global attack detection (GAD) system that serializes a bad data detector and a novel secondary attack detector designed based on unique TPS characteristics. With intact position data of trains, our detection system can effectively detect the FDI attacks on trains' voltage and current measurements even if the attacker has full and accurate knowledge of the TPS, attack detection, and real-time system state. In particular, the GAD system features an adaptive mechanism that ensures low false positive and negative rates in detecting the attacks under noisy system measurements. Extensive simulations driven by realistic running profiles of trains verify that a TPS setup is vulnerable to the FDI attacks, but these attacks can be detected effectively by the proposed GAD while ensuring a low false positive rate.Comment: IEEE/IFIP DSN-2016 and ACM Trans. on Cyber-Physical System

Mechanical effects of cell size and wall thickness on the rubber wood honeycomb sandwich composites

Malaysia has one of the biggest rubber wood plantations to meet the latex demand from worldwide where rubber trees are utilised in the furniture industry. Due to high volume of residue produced from processing the wood, sawdust and wood flour are processed into so called green wood plastic composite products such as medium density fibreboard (MDF) and particle board. In this research, it is aimed to optimise the applications of solid rubber wood as a structural member in the form of sandwich composite. It deserves more significant role in the engineering field apart from furniture industry to decrease the dependency on synthetic woods. It opens up a new economy source for the rubber wood. This also associates with the research trend to promote green and biodegradable natural material. However, geometrical parameters on rubber wood (eg. cell wall thickness and cell size) have not been discussed previously that determine the mechanical performance of the sandwich composites by using natural solid wood and its failure mode in terms of adhesion behaviour between the facesheet and its honeycomb. Hand lay-up technique assisted by vacuum bagging technique at room temperature carried out for a rubber wood based honeycomb composites with two layers of glass fibre facesheets on each side was fabricated with 1mm, 1.5mm, 2mm and 3mm cell wall. Meanwhile, the cell size of core was 7mm, 7.5mm, 8mm and 9 mm with a standard core height of 10mm. In order to verify such geometrical parameters on rubber wood, it was tested with composites using pine and balsa wood core. Tests carried out were flexural test (ASTM C393), compression test (ASTM C365), flatwise tensile test (ASTM C297) and climbing drum peel (ASTM D1781). By increasing the cell wall thickness, the flexural performance increase by 12.32% (rubber wood), 43.60% (pine) and 113.98% (balsa) from 1mm to 3mm as well as increase of 11% (rubber wood), 18% (pine) and 38% (balsa) in flatwise compression. Rubber wood composites with 3mm cell wall improve by 17.41% in flatwise tensile and only 1% difference in climbing drum peel test (with reduced density in honeycomb structure) when compared with SWWS. With the increase in cell size from 7mm to 9mm, the flexural properties dropped 18.36% (rubber wood), 41.14% (pine) and 10.20% (balsa) while the flatwise compression properties dropped 22.26% (rubber wood), 30.68% (pine) but increased 97.91% for balsa. Using rubber wood honeycomb from 7mm to 9mm, the flatwise tensile properties dropped 30.41% and 38.42% (compared with SWWS) in climbing drum peel test. This research has addressed the research gap on the feasibility of using rubber wood as the natural core in honeycomb composite as a structural member that serves as an alternative to synthetic wood plastic composites for greener environment. The geometrical parameters are suitable for wood core materials in hardwood and softwood categories. As such, it has successfully utilised RWC7W3 in developing a new platform as a prototype for electric scooter

Bright light therapy as part of a multicomponent management program improves sleep and functional outcomes in delirious older hospitalized adults.

ObjectiveDelirium is associated with poor outcomes following acute hospitalization. A specialized delirium management unit, the Geriatric Monitoring Unit (GMU), was established. Evening bright light therapy (2000-3000 lux; 6-10 pm daily) was added as adjunctive treatment, to consolidate circadian activity rhythms and improve sleep. This study examined whether the GMU program improved sleep, cognitive, and functional outcomes in delirious patients.MethodA total of 228 patients (mean age = 84.2 years) were studied. The clinical characteristics, delirium duration, delirium subtype, Delirium Rating Score (DRS), cognitive status (Chinese Mini-Mental State Examination), functional status (modified Barthel Index [MBI]), and chemical restraint use during the initial and predischarge phase of the patient's GMU admission were obtained. Nurses completed hourly 24-hour patient sleep logs, and from these, the mean total sleep time, number of awakenings, and sleep bouts (SB) were computed.ResultsThe mean delirium duration was 6.7 ± 4.6 days. Analysis of the delirium subtypes showed that 18.4% had hypoactive delirium, 30.2% mixed delirium, and 51.3% had hyperactive delirium. There were significant improvements in MBI scores, especially for the hyperactive and mixed delirium subtypes (P < 0.05). Significant improvements were noted on the DRS sleep-wake disturbance subscore, for all delirium-subtypes. The mean total sleep time (7.7 from 6.4 hours) (P < 0.05) and length of first SB (6.0 compared with 5.3 hours) (P < 0.05) improved, with decreased mean number of SBs and awakenings. The sleep improvements were mainly seen in the hyperactive delirium subtype.ConclusionThis study shows initial evidence for the clinical benefits (longer total sleep time, increased first SB length, and functional gains) of incorporating bright light therapy as part of a multicomponent delirium management program. The benefits appear to have occurred mainly in patients with hyperactive delirium, which merits further in-depth, randomized controlled studies