Series compensation method to mitigate harmonics and voltage sags and swells

The use of a series compensator (SC) to improve power quality is investigated. The role of the compensator is not only to mitigate the effects of voltage sag and swell, but also to control the level of harmonic distortions in the network. This is accomplished through extension of the voltage injection scheme of the SC by the incorporation of load current feedback and an external inductive filter. The compensation process is accompanied by an exchange of energy between the SC and the external network. Through a phase adjustment technique, it is shown that the voltage quality across the terminals of the protected load can be controlled. Simulation studies, supported by laboratory experiments, show that the resulting series compensation scheme is effective in improving the supply quality of the power system.     

Built-In Self-Testing RAM: A Practical Alternative

The article investigates the design of a built-in self-testing RAM as an economical way, in terms of silicon area overhead, to test memories?more economical than the use of external testers. The design of a BIST static RAM is given, along with design decisions, retrospectives on how design could have used the area even more efficiently, and results of implementation. The extra silicon area used by the BIST hardware for 64K static memories is only five percent; for larger memories, it is less. BIST RAM, then, is a practical alternative, especially since testing can be done even during burn-in without the aid of an expensive external tester.     

Discharge planning in a community hospital--a multidisciplinary approach

OBJECTIVES: Osteoporosis is common in subjects over 70 years of age. Likewise, the incidence of monogammapathies of undetermined signification (MGUS) increases with age. We conducted this study to determine whether the biological and histomorphometric characteristics of osteoporosis in patients with MGUS are different from those in primary osteoporosis and to ascertain whether any cause and effect relationships could exist between MGUS and osteoporosis, excluding signs of active myeloma. PATIENTS AND METHODS: Serum and urinary phosphorus and calcium, histomorphometric measurements, hormone levels and serum cytokines (IL1, IL6 and TNF alpha) were determined in 7 patients (mean age 71.8 years, 2 men and 5 women) with MGUS associated with osteoporosis with vertebral fractures (OP) and compared with those in 7 osteoporosis patients without MGUS matched for age, sex, and osteoporosis severity and 7 other age and sex matched patients with MGUS without OS. The MGUS + PS patients were followed for 9 years (4.5 to 20) so slowly progressive myeloma could be excluded. RESULTS: Cytokine levels were the same in the three groups of patients but MGUS + OP patients had higher urinary calcium levels (ca/cr = 0.21 +/- 0.08 vs 0.12 +/- 0.1 (OP) and 0.13 (MGUS); p = 0.04), decreased osteocalcin levels (7 +/- 4.6 ng/ml vs. 12 +/- 4 (OP) and 11.5 +/- 5 (MGUS); p = 0.01) and increased surface resorption (8 +/- 1.4 vs. 3.6 +/- 1.2 (OP) and 5.5 +/- 1.7 (MGUS); p = 0.05). DISCUSSION: It has been demonstrated that MGUS in patients with increased resorption and lower osteocalcin levels frequently progresses to active myeloma. The question is raised as to whether, in certain cases of MGUS, in situ stimulation of bone cells by monoclonal plasma cells could exist without ongoing transformation to active myeloma.     

Does parental job insecurity matter? Money anxiety, money motives, and work motivation.

A structural model focusing on the spillover effect of parental perceived job insecurity on money anxiety was developed and tested. The crossover effect of parents' money anxiety on their children's money anxiety, money motives, and motivation to work was also examined. Data were collected from a sample of undergraduates and their parents. Results of structural equation modeling analyses supported a spillover effect of paternal perceived job insecurity on paternal money anxiety. However, maternal perceived job insecurity was not significantly associated with maternal money anxiety. Results also supported a crossover effect of parental money anxiety on youths' money anxiety. Youths' money anxiety was significantly related to youths' negative money motives. In turn, youths' negative money motives were associated with their intrinsic motivation to work. Implications of the findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterisation of calamansi (Citrus microcarpa). Part II: Volatiles,physicochemical properties and non-volatiles in the juice

Calamansi juices from three countries (Malaysia, the Philippines and Vietnam) were characterised through measuring volatiles, physicochemical properties and non-volatiles (sugars, organic acids and phenolic acids). The volatile components of manually squeezed calamansi juices were extracted using dichloromethane and headspace solid-phase microextraction, and then analysed using gas chromatography–mass spectrometry/flame ionisation detector, respectively. A total of 60 volatile compounds were identified. The results indicated that the Vietnam calamansi juice contained the highest amount of volatiles. Two principal components obtained from principal component analysis (PCA) represented 89.65% of the cumulative total variations of the volatiles. Among the non-volatile components, these three calamansi juices could be, to some extent, differentiated according to fructose and glucose concentrations. Hence, this study of calamansi juices could lead to a better understanding of calamansi fruits.     

Effect of beam profile on the cross talk of land and groove recording

Numerical analyses were conducted to simulate the effects of different Gaussian-weighted beams and disk geometries on the read-out signal cross talk of land and groove recording of phase-change optical disk systems. The optimized groove depth, which yields a minimum cross-talk noise, differs for different Gaussian-weighted beams and different track pitches. This beam profile dependence of the optimum groove depth is undesirable for practical application of this technique, because different optical systems may have different beam profiles at the lens aperture plane. It is found that this effect can be reduced to a certain extent by introduction of an appropriate shading band filter.     

Effective design of barrier enclosure to contain aerosol emissions from COVID-19 patients

Facing shortages of personal protective equipment, some clinicians have advocated the use of barrier enclosures (typically mounted over the head, with and without suction) to contain aerosol emissions from coronavirus disease 2019 (COVID-19) patients. There is, however, little evidence for its usefulness. To test the effectiveness of such a device, we built a manikin that can expire micron-sized aerosols at flow rates close to physiological conditions. We then placed the manikin inside the enclosure and used a laser sheet to visualize the aerosol leaking out. We show that with sufficient suction, it is possible to effectively contain aerosol from the manikin, reducing aerosol exposure outside the enclosure by 99%. In contrast, a passive barrier without suction only reduces aerosol exposure by 60%.     

Optimum Trajectory Switching Control for Series-Parallel Resonant Converter

The series-parallel resonant converter (SPRC) is known to have combined merits of the series resonant converter (SRC) and PRC. However, the SPRC has a three-element LCC structure with complex transient dynamics, and without control of the resonant circuit's dynamics, the converter's closed-loop bandwidth to switching-frequency ratio will be much reduced compared to that of pulsewidth-modulation (PWM) converters. This paper presents the optimal trajectory enabling any SPRC's steady state be achieved within one cycle. Dynamics using the state-plane analysis is presented, and the optimal state trajectory for transients is derived. Experimental results with comparison to frequency control show much reduced resonant circuit response time for step changes in output voltage. This improved resonant circuit control allows subsequent current and voltage-loop controls of the SPRC to be treated as that of a conventional PWM voltage source     

一种新型渗硼剂的研制

渗硼是一种表面强化工艺,电厂金属材料经渗硼处理后不仅表面硬度高、耐磨性好,而且还有一定的抗高温氧化性和耐蚀性。本文通过正交设计及快速登高法精选出了一种新型渗硼剂的配方:80％氯化稀土 17％Na_2SIF_6 11％Si-Ca-Fe 26％Na_2B_4O_7 38％石墨,经试验该渗剂具有渗速快、渗后松散、试样表面清洁、松装比容大等优点。