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Shock wave interaction with solid wedges has been an area of much research in past decades, but so far very few results have been obtained for shock wave reflection off liquid wedges. In this study, numerical simulations are performed using the inviscid Euler equations and the stiffened gas equation of state to study the transition angles, reflection patterns and triple point trajectory angles of shock reflection off solid and water wedges. Experiments using an inclined shock tube are also performed and schlieren photography results are compared to simulations. Results show that the transition angles for the water wedge cases are within 5.3 % and 9.2 %, for simulations and experiments respectively, compared to results obtained with the theoretical detachment criterion for solid surfaces. Triple point trajectory angles are measured and compared with analytic solutions, agreement within
is shown for the water wedge cases. The transmitted wave in the water observed in the simulation is quantitatively studied, and two different scenarios are found. For low incident shock Mach numbers,
and 2, no shock wave is formed in the water but a precursor wave is induced ahead of the incident shock wave and passes the information from the water back into the air. For high incident shock Mach numbers,
and 4, precursor waves no longer appear but instead a shock wave is formed in the water and attached to the Mach stem at every instant. The temperature field in the water is measured in the simulation. For strong incident shock waves, e.g.
, the temperature increment in the water is up to 7.3 K.
Aging is accompanied by cognitive decline that is escalated in older adults reporting extreme sleep duration. Social relationships can influence health outcomes and thus may qualify the association between sleep duration and cognitive function. The present study examines the moderating effects of marital status, household size, and social network with friends and relatives on the sleep–cognition association among older adults.
Data (N = 4,169) came from the Social Isolation, Health, and Lifestyles Survey, a nationally representative survey of community-dwelling older Singaporeans (≥ 60 years). Sleep duration and social relationships were self-reported. Cognitive function was assessed with the Short Portable Mental Status Questionnaire.
Regression analysis revealed that the inverted U-shaped association between sleep duration and cognitive function was less profound among older adults who were married (vs. unmarried) and those who had stronger (vs. weaker) social networks. In contrast, it was more prominent among individuals who had more (vs. fewer) household members.
Being married and having stronger social networks may buffer against the negative cognitive impact of extreme sleep duration. But larger household size might imply more stress for older persons, and therefore strengthen the sleep duration–cognitive function association. We discuss the potential biological underpinnings and the policy implications of the findings. Although our findings are based on a large sample, replication studies using objective measures of sleep duration and other cognitive measures are needed.
Dementia is a neurodegenerative syndrome that interferes with multiple aspects of life, including cognition, daily functioning, and behavior. Despite the large heterogeneity in symptom development, these three domains are seldom studied simultaneously. This study investigates how trajectories of these domains are interrelated within individuals over time, and how they in turn are related to dementia severity and quality of life (QoL).
We used data from a longitudinal clinical cohort study, including 331 dementia patients. Cognitive status was measured using the Mini-Mental State Examination, daily functioning was measured with the disability assessment for dementia and neuropsychiatric symptoms (NPS) were scored using the neuropsychiatric inventory. We investigated the relationships in the time course of the various dementia domains using random effects multilevel models and parallel-process growth models.
Changes in cognition and daily functioning were highly correlated over time (r = 0.85, p < 0.01), as were changes in NPS and functioning (r = −0.60, p < 0.01), while changes in cognition and NPS were not (r = −0.20, p = 0.06). All three domains were strongly associated with dementia severity over time (p < 0.01). Decreased functioning and increased NPS were both associated with decreased QoL (β = 2.97, p < 0.01 and β = −2.41, p < 0.01, respectively), while cognition was not (β = 0.01, p = 0.93).
This study demonstrates the heterogeneity of dementia progression between individuals and between different dementia domains within individuals. To improve our understanding of dementia progression, future research should embrace a broader perspective encompassing multiple outcome measures along with the patient's profile, including neurological factors as well as physical, social, and psychiatric health.
We construct the complete network of 26,681 majority opinions written by the U.S. Supreme Court and the cases that cite them from 1791 to 2005. We describe a method for using the patterns in citations within and across cases to create importance scores that identify the most legally relevant precedents in the network of Supreme Court law at any given point in time. Our measures are superior to existing network-based alternatives and, for example, offer information regarding case importance not evident in simple citation counts. We also demonstrate the validity of our measures by showing that they are strongly correlated with the future citation behavior of state courts, the U.S. Courts of Appeals, and the U.S. Supreme Court. In so doing, we show that network analysis is a viable way of measuring how central a case is to law at the Court and suggest that it can be used to measure other legal concepts.
A new approach is proposed to analyze Bremsstrahlung X-rays that are emitted from laser-produced plasmas (LPP) and are measured by a stack type spectrometer. This new method is based on a spectral tomographic reconstruction concept with the variational principle for optimization, without referring to the electron energy distribution of a plasma. This approach is applied to the analysis of some experimental data obtained at a few major laser facilities to demonstrate the applicability of the method. Slope temperatures of X-rays from LPP are determined with a two-temperature model, showing different spectral characteristics of X-rays depending on laser properties used in the experiments.
A time-series CCD photometric survey of variable stars in open clusters has been in progress using 1.8-m telescope at the Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. We present preliminary results of time series photometry for the intermediate-age open cluster NGC 2301.
We report on the results of CCD photometric observations of the open cluster NGC 2539. Eight new variable stars have been found in the observed field of this cluster. However, no γ Doradus-type variability was found among the member stars.
Through time-series CCD photometry of the globular cluster M 53, we have discovered eight new SX Phoenicis type stars. All the new SX Phoenicis stars are located in the blue straggler star region in the color-magnitude diagram of M 53. In addition, we have obtained light curves for 45 known RR Lyrae stars.
This paper presents a new cooperative object transportation technique using parallel line formation with a circular shift. Typical areas of research in relation to object transportation are grasping, pushing, and caging techniques, but these require precise grasping behaviors, iterative motion correction according to the object pose, and the real-time acquisition of the object shape, respectively. In this paper, the proposed technique does not need to consider the shape or the pose of objects, and equipped tools are not necessary for object transportation because objects are transported by pushing behavior only. Multiple robots create parallel line formation using a virtual electric dipole field and then push multiple objects into the formation. This parallel line is extended to the goal using cyclic motion by the robots and the objects are transported to the goal by pushing behavior. The above processes are decentralized and activated based on the finite state machine of each robot. Simulations and practical experiments are presented to verify the proposed technique.
Behavioral and psychological symptoms of dementia (BPSD) are often considered to be the greatest challenge in dementia care, leading to increased healthcare costs, caregiver burden, and placement into care facilities. With potential for pharmacological intervention to exacerbate behaviors or even lead to mortality, the development and rigorous testing of non-pharmacological interventions is vital. A pilot of the Tailored Activities Program (TAP) for reducing problem behaviors in people with dementia was conducted in the United States with promising results. This randomized trial will investigate the effectiveness of TAP for reducing the burden of BPSD on persons with dementia and family caregivers within an Australian population. This trial will also examine the cost-effectiveness and willingness to pay for TAP compared with a control group.
This randomized trial aims to recruit 180 participant dyads of a person with dementia and their caregivers. Participants will have a diagnosis of dementia, exhibit behaviors as scored by the Neuropsychiatric Inventory, and the caregiver must have at least 7 h per week contact. Participants will be randomly allocated to intervention (TAP) or control (phone-based education sessions) groups, both provided by a trained occupational therapist. Primary outcome measure will be the revised Neuropsychiatric Inventory – Clinician rating scale (NPI-C) to measure BPSD exhibited by the person with dementia.
This trial investigates the effectiveness and cost-effectiveness of TAP within an Australian population. Results will address a significant gap in the current Australian community-support base for people living with dementia and their caregivers.
Hierarchically porous materials are of interest in a wide range of applications. If the materials are electronic or ionic conductors such materials are of interest as electrodes for use in fuel cells, flow batteries, electrocatalysis, and pseudo/supercapacitors. We have demonstrated the synthesis of hierarchically porous carbon, metal and metal oxide monoliths. Hierarchically porous silica with porosity at three length scales: 0.5-30 micrometer, 200-500 nm, and 3-8 nm, is used as a template to form these materials. The porosity of the silica template is produced by spinodal decomposition (0.5-30 micrometer), particle agglomeration (200-500 nm) and addition of surfactant or block copolymer (3-8 nm). Nanocasting: replication of all or part of the structure via one of a number of chemical replication techniques has been used to produce the carbon, metal oxide and metal replicas. The final surface areas of the materials can be as high as 1200 m2/g for carbon replicas, and >300 m2/g for metals and metal oxides. The use of the nanocasting technique allows for formation of materials that are compositionally or spatially heterogeneous.
We report here results on the synthesis and characterization of hierarchically porous monoliths of carbon and, nickel and the use of some of these monoliths in catalysis and electrochemical capacitors.
A new excimer laser annealing method is proposed in order to produce the poly-Si film with low defect density and large grain, by combining the selective Si ionimplantation and excimer laser annealing. Selective Si ion-implantation is employed to form artificial nucleation seeds in a-Si film prior to excimer laser annealing in order to increase the nucleation probability. The grain boundary location in poly-Si film has been controlled through implantation mask, and the grain size around micrometer order is obtained without any other process. TEM result shows that grain boundary is controlled according to mask pattern and the crystallinity of the poly-Si film is improved.
A new excimer laser recrystallization method of amorphous silicon is proposed to increase the grain size and control the grain boundary locations in polycrystalline silicon films. The proposed method is based on the lateral grain growth which occurs at the interface between molten and unmolten regions. To obtain selectively molten regions, the proposed method employs aluminum patterns on amorphous silicon. The aluminum patterns act as the beam shield during the laser irradiation as well as the lateral heat sink during the solidification period. The high reflectance of aluminum at the wavelength of XeCl excimer laser offers stable beam shielding property, and the high thermal conductivity enhances the lateral heat flow by the quick draining of laterally propagated heat. TEM observation has revealed that the well arranged large grains were successfully obtained.
Near edge X-ray absorption spectra (XANES) have been obtained from the Ti K-edge for several series of titanium silicide samples produced by different techniques. Samples were fabricated by depositing Ti on silicon wafers and subsequently annealing them up to temperatures from 100°C to 900°C in UHV, vacuum furnace, or in a Rapid Thermal Annealing system. Measurements were done in the fluorescence and total electron yield modes. The XANES measurements were correlated with Raman scattering measurements. The XANES data of several reference compounds were obtained, and the data showed a high sensitivity to changes in the film structure. Ti metallic bonding and Ti-Si bonds can be distinguished and their evolution as a function of annealing is related to previous results. For the samples with increased impurities, Ti regions were stable at higher temperatures. The XANES spectra of samples annealed under N2 indicate the formation of a surface nitride.
Striking progress in the development of II-VI semiconductor heterostructures, coupled with seminal advances in doping, has very recently led to the first demonstration of blue and blue/green diode lasers operating from cryogenic to room temperature. The active region in these devices was based on the (Zn, Cd)Se/ZnSe multiple quantum wells (MQW) which had earlier been actively studied as a candidate for laser medium by optical pumping techniques. We report on the performance of such MQW diode lasers with emphasis on structural versatility in terms of preparation on both p-type and n-type GaAs substrates, and where sulfur is or is not incorporated for blue/green color lasing. In this work we have obtained pulsed, high power, high quantum efficiency laser emission up to near room temperature conditions. Efficient LED devices are described which operate in the blue (494nm) at room temperature.
We have obtained continuous-wave laser operation at room temperature from a (Zn,Mg)(S,Se)-based Il-VI separate-confinement heterostructure where injection of holes into the p-type quaternary was achieved through the employment of a Zn(Se,Te) graded-bandgap contact. The laser devices exhibit threshold current densities of below 300 A/cm2 and voltages below 6 V. Issues related to the control of the growth of the quaternary (Zn,Mg)(S,Se) compound, and a proposal to further reducing the laser operating voltage will also be described.
Superlattices and quantum wells of Znl-xCdxSe/ZnSe,
and heterostructures based on ZnSe/CdSe digital alloys have been grown by
molecular beam epitaxy (MBE). Their optical properties were studied with
particular emphasis on excitonic absorption and photopumped stimulated
emission. Excitonic absorption is easily observable up to 400 K, and is
characterized by extremely large absorption coefficients (α =
2×105cm−1). Optically pumped lasing action is
obtained at room temperature with a typical threshold intensity of 100
kW/cm2. The lasing mechanism in these II-VI quantum wells
appears to be quite different from that in the better studied III-V
materials: in our case, the onset of stimulated emission occurs
before the saturation of the excitonic absorption, and
the stimulated emission occurs at an energy lower than that
of the excitonic absorption.