Replacing Copper with New Carbon Nanomaterials in Electrical Machine Windings

Electrical machines have significant improvement potential. Nevertheless, the field is characterized by incremental innovations. Admittedly, steady improvement has been achieved, but no breakthrough development. Radical development in the field would require the introduction of new elements, such that may change the whole electrical machine industry system. Recent technological advancements in nanomaterials have opened up new horizons for the macroscopic application of carbon nanotube (CNT) fibres. With values of 100 MS/m measured on individual CNTs, CNT fibre materials hold promise for conductivities far beyond those of metals. Highly conductive, lightweight and strong CNT yarn is finally within reach; it could replace copper as a potentially better winding material. Although not yet providing low resistivity, the newest CNT yarn offers attractive perspectives for accelerated efficiency improvement of electrical machines. In this article, the potential for using new CNT materials to replace copper in machine windings is introduced. It does so, firstly, by describing the environment for a change that could revolutionize the industry and, secondly, by presenting the breakthrough results of a prototype construction. In the test motor, which is to our knowledge the first in its kind, the presently most electrically conductive carbon nanotube yarn replaces usual copper in the windings.

Electrical field stimulation improves bone mineral density in ovariectomized rats

Osteoporosis and its consequent fractures are a great social and medical problem mainly occurring in post-menopausal women. Effective forms of prevention and treatment of osteoporosis associated with lower costs and the least side effects are needed. Electrical fields are able to stimulate osteogenesis in fractures, but little is known about their action on osteoporotic tissue. The aim of the present study was to determine by bone densitometry the effects of electrical stimulation on ovariectomized female Wistar rats. Thirty rats (220 ± 10 g) were divided into three groups: sham surgery (SHAM), bilateral ovariectomy (OVX) and bilateral ovariectomy + electrical stimulation (OVX + ES). The OVX + ES group was submitted to a 20-min session of a low-intensity pulsed electrical field (1.5 MHz, 30 mW/cm²) starting on the 7th day after surgery, five times a week (total = 55 sessions). Global, spine and limb bone mineral density were measured by dual-energy X-ray absorptiometry (DXA Hologic 4500A) before surgery and at the end of protocol (84 days after surgery). Electrical stimulation improved (P < 0.05) global (0.1522 ± 0.002), spine (0.1502 ± 0.003), and limb (0.1294 ± 0.003 g/cm²) bone mineral density compared to OVX group (0.1447 ± 0.001, 0.1393 ± 0.002, and 0.1212 ± 0.001, respectively). The OVX + ES group also showed significantly higher global bone mineral content (9.547 ± 0.114 g) when compared to both SHAM (8.693 ± 0.165 g) and OVX (8.522 ± 0.207 g) groups (P < 0.05). We have demonstrated that electrical fields stimulate osteogenesis in ovariectomized female rats. Their efficacy in osteoporosis remains to be demonstrated.

The effect of an aerobic training program on the electrical remodeling of the heart: high-frequency components of the signal-averaged electrocardiogram are predictors of the maximal aerobic power

Increased heart rate variability (HRV) and high-frequency content of the terminal region of the ventricular activation of signal-averaged ECG (SAECG) have been reported in athletes. The present study investigates HRV and SAECG parameters as predictors of maximal aerobic power (VO2max) in athletes. HRV, SAECG and VO2max were determined in 18 high-performance long-distance (25 ± 6 years; 17 males) runners 24 h after a training session. Clinical visits, ECG and VO2max determination were scheduled for all athletes during thew training period. A group of 18 untrained healthy volunteers matched for age, gender, and body surface area was included as controls. SAECG was acquired in the resting supine position for 15 min and processed to extract average RR interval (Mean-RR) and root mean squared standard deviation (RMSSD) of the difference of two consecutive normal RR intervals. SAECG variables analyzed in the vector magnitude with 40-250 Hz band-pass bi-directional filtering were: total and 40-µV terminal (LAS40) duration of ventricular activation, RMS voltage of total (RMST) and of the 40-ms terminal region of ventricular activation. Linear and multivariate stepwise logistic regressions oriented by inter-group comparisons were adjusted in significant variables in order to predict VO2max, with a P < 0.05 considered to be significant. VO2max correlated significantly (P < 0.05) with RMST (r = 0.77), Mean-RR (r = 0.62), RMSSD (r = 0.47), and LAS40 (r = -0.39). RMST was the independent predictor of VO2max. In athletes, HRV and high-frequency components of the SAECG correlate with VO2max and the high-frequency content of SAECG is an independent predictor of VO2max.

Changes in types of muscle fibers induced by transcutaneous electrical stimulation of the diaphragm of rats

The objective of the present study was to assess the effect of transcutaneous electrical diaphragmatic stimulation (TEDS) on different types of diaphragm muscle fibers. Male Wistar rats (8-12 weeks old) were divided into 2 experimental groups (N = 8 in each group): 1) control, 2) animals submitted to TEDS [frequency = 50 Hz; T ON/T OFF (contraction/relaxation time) = 2/2 s; pulse duration = 0.4 ms, intensity = 5 mA with a 1 mA increase every 3 min for 20 min] for 7 days. After completing this treatment period, the I, IIA, IIB, and IID diaphragm muscle fibers were identified using the mATPase technique. Statistical analysis consisted of the normality, homoscedasticity and t-tests (P < 0.05). There was a 19.6% (P < 0.05) reduction in the number of type I fibers and a 49.7% increase (P < 0.05) in type IID fibers in the TEDS group compared with the control group. An important result of the present study was that electrical stimulation with surface electrodes was efficient in altering the distribution of fibers in diaphragm muscle. This therapeutic resource could be used in the treatment of respiratory muscle alterations.

Nutritional status and body composition after 6 months of patients switching from continuous ambulatorial peritoneal dialysis to automated peritoneal dialysis

Our objective was to determine if automated peritoneal dialysis (APD) leads to changes in nutritional parameters of patients treated by continuous ambulatory peritoneal dialysis (CAPD). Twenty-six patients (15 males; 50.5 ± 14.3 years) were evaluated during CAPD while training for APD and after 3 and 6 months of APD. Body fat was assessed by the sum of skinfold thickness and the other body compartments were assessed by bioelectrical impedance. During the 6-month follow-up, 12 patients gained more than 1 kg (GW group), 8 patients lost more than 1 kg (LW group), and 6 patients maintained body weight (MW group). Except for length on dialysis that was longer for the LW group compared with the GW group, no other differences were found between the groups at baseline. After 6 months on APD, the LW group had a reduction in body fat (24.5 ± 7.7 vs 22.1 ± 7.3 kg; P = 0.01), body cell mass (22.6 ± 6.2 vs 21.6 ± 5.8 kg, P = 0.02) and phase angle (5.4 ± 0.9 vs 5.1 ± 0.8 degrees, P = 0.004). In the GW group, body fat (25 ± 7.6 vs 27.2 ± 7.6 kg, P = 0.001) and body cell mass (20.1 ± 3.9 vs 20.8 ± 4.0 kg, P = 0.05) were increased. In the present study, different patterns of change in body composition were found. The length of previous dialysis treatment seems to be the most important factor in determining these nutritional modifications.

Acute and chronic electrical activation of baroreceptor afferents in awake and anesthetized subjects

Electrical stimulation of baroreceptor afferents was used in the 1960's in several species, including human beings, for the treatment of refractory hypertension. This approach bypasses the site of baroreceptor mechanosensory transduction. Chronic electrical stimulation of arterial baroreceptors, particularly of the carotid sinus nerve (Hering's nerve), was proposed as an ultimate effort to treat refractory hypertension and angina pectoris due to the limited nature of pharmacological therapy available at that time. Nevertheless, this approach was abandoned in the early 1970's due to technical limitations of implantable devices and to the development of better-tolerated antihypertensive medications. More recently, our laboratory developed the technique of electrical stimulation of the aortic depressor nerve in conscious rats, enabling access to hemodynamic responses without the undesirable effect of anesthesia. In addition, electrical stimulation of the aortic depressor nerve allows assessment of the hemodynamic responses and the sympathovagal balance of the heart in hypertensive rats, which exhibit a well-known decrease in baroreflex sensitivity, usually attributed to baroreceptor ending dysfunction. Recently, there has been renewed interest in using electrical stimulation of the carotid sinus, but not the carotid sinus nerve, to lower blood pressure in conscious hypertensive dogs as well as in hypertensive patients. Notably, previous undesirable technical outcomes associated with electrical stimulation of the carotid sinus nerve observed in the 1960's and 1970's have been overcome. Furthermore, promising data have been recently reported from clinical trials that evaluated the efficacy of carotid sinus stimulation in hypertensive patients with drug resistant hypertension.

Effects of different frequencies of transcutaneous electrical nerve stimulation on venous vascular reactivity

Transcutaneous electrical nerve stimulation (TENS) is a type of therapy used primarily for analgesia, but also presents changes in the cardiovascular system responses; its effects are dependent upon application parameters. Alterations to the cardiovascular system suggest that TENS may modify venous vascular response. The objective of this study was to evaluate the effects of TENS at different frequencies (10 and 100 Hz) on venous vascular reactivity in healthy subjects. Twenty-nine healthy male volunteers were randomized into three groups: placebo (n=10), low-frequency TENS (10 Hz, n=9) and high-frequency TENS (100 Hz, n=10). TENS was applied for 30 min in the nervous plexus trajectory from the superior member (from cervical to dorsal region of the fist) at low (10 Hz/200 μs) and high frequency (100 Hz/200 μs) with its intensity adjusted below the motor threshold and intensified every 5 min, intending to avoid accommodation. Venous vascular reactivity in response to phenylephrine, acetylcholine (endothelium-dependent) and sodium nitroprusside (endothelium-independent) was assessed by the dorsal hand vein technique. The phenylephrine effective dose to achieve 70% vasoconstriction was reduced 53% (P<0.01) using low-frequency TENS (10 Hz), while in high-frequency stimulation (100 Hz), a 47% increased dose was needed (P<0.01). The endothelium-dependent (acetylcholine) and independent (sodium nitroprusside) responses were not modified by TENS, which modifies venous responsiveness, and increases the low-frequency sensitivity of α1-adrenergic receptors and shows high-frequency opposite effects. These changes represent an important vascular effect caused by TENS with implications for hemodynamics, inflammation and analgesia.

Influence of transcutaneous electrical stimulation on heterotopic ossification: an experimental study in Wistar rats

Heterotopic ossification (HO) is a metaplastic biological process in which there is newly formed bone in soft tissues, resulting in joint mobility deficit and pain. Different treatment modalities have been tried to prevent HO development, but there is no consensus on a therapeutic approach. Since electrical stimulation is a widely used resource in physiotherapy practice to stimulate joint mobility, with analgesic and anti-inflammatory effects, its usefulness for HO treatment was investigated. We aimed to identify the influence of electrical stimulation on induced HO in Wistar rats. Thirty-six male rats (350-390 g) were used, and all animals were anesthetized for blood sampling before HO induction, to quantify the serum alkaline phosphatase. HO induction was performed by bone marrow implantation in both quadriceps of the animals, which were then divided into 3 groups: control (CG), transcutaneous electrical nerve stimulation (TENS) group (TG), and functional electrical stimulation (FES) group (FG) with 12 rats each. All animals were anesthetized and electrically stimulated twice per week, for 35 days from induction day. After this period, another blood sample was collected and quadriceps muscles were bilaterally removed for histological and calcium analysis and the rats were killed. Calcium levels in muscles showed significantly lower results when comparing TG and FG (P<0.001) and between TG and CG (P<0.001). Qualitative histological analyses confirmed 100% HO in FG and CG, while in TG the HO was detected in 54.5% of the animals. The effects of the muscle contractions caused by FES increased HO, while anti-inflammatory effects of TENS reduced HO.

Modeling Energy Futures Returns With Markov Regime Switching Model

Financial time series have a tendency of abruptly changing their behavior and maintain this behavior for several consecutive periods, and commodity futures returns are not an exception. This quality proposes that nonlinear models, as opposed to linear models, can more accurately describe returns and volatility. Markov regime switching models are able to match this behavior and have become a popular way to model financial time series. This study uses Markov regime switching model to describe the behavior of energy futures returns on a commodity level, because studies show that commodity futures are a heterogeneous asset class. The purpose of this thesis is twofold. First, determine how many regimes characterize individual energy commodities’ returns in different return frequencies. Second, study the characteristics of these regimes. We extent the previous studies on the subject in two ways: We allow for the possibility that the number of regimes may exceed two, as well as conduct the research on individual commodities rather than on commodity indices or subgroups of these indices. We use daily, weekly and monthly time series of Brent crude oil, WTI crude oil, natural gas, heating oil and gasoil futures returns over 1994–2014, where available, to carry out the study. We apply the likelihood ratio test to determine the sufficient number of regimes for each commodity and data frequency. Then the time series are modeled with Markov regime switching model to obtain the return distribution characteristics of each regime, as well as the transition probabilities of moving between regimes. The results for the number of regimes suggest that daily energy futures return series consist of three to six regimes, whereas weekly and monthly returns for all energy commodities display only two regimes. When the number of regimes exceeds two, there is a tendency for the time series of energy commodities to form groups of regimes. These groups are usually quite persistent as a whole because probability of a regime switch inside the group is high. However, individual regimes in these groups are not persistent and the process oscillates between these regimes frequently. Regimes that are not part of any group are generally persistent, but show low ergodic probability, i.e. rarely prevail in the market. This study also suggests that energy futures return series characterized with two regimes do not necessarily display persistent bull and bear regimes. In fact, for the majority of time series, bearish regime is considerably less persistent. Rahoituksen aikasarjoilla on taipumus arvaamattomasti muuttaa käyttäytymistään ja jatkaa tätä uutta käyttäytymistä useiden periodien ajan, eivätkä hyödykefutuurien tuotot tee tähän poikkeusta. Tämän ominaisuuden johdosta lineaaristen mallien sijasta epälineaariset mallit pystyvät tarkemmin kuvailemaan esimerkiksi tuottojen jakauman parametreja. Markov regiiminvaihtomallit pystyvät vangitsemaan tämän ominaisuuden ja siksi niistä on tullut suosittuja rahoituksen aikasarjojen mallintamisessa. Tämä tutkimus käyttää Markov regiiminvaihtomallia kuvaamaan yksittäisten energiafutuurien tuottojen käyttäytymistä, sillä tutkimukset osoittavat hyödykefutuurien olevan hyvin heterogeeninen omaisuusluokka. Tutkimuksen tarkoitus on selvittää, kuinka monta regiimiä tarvitaan kuvaamaan energiafutuurien tuottoja eri tuottofrekvensseillä ja mitkä ovat näiden regiimien ominaisuudet. Aiempaa tutkimusta aiheesta laajennetaan määrittämällä regiimien lukumäärä tilastotieteellisen testauksen menetelmin sekä tutkimalla energiafutuureja yksittäin; ei indeksi- tai alaindeksitasolla. Tutkimuksessa käytetään päivä-, viikko- ja kuukausiaikasarjoja Brent-raakaöljyn, WTI-raakaöljyn, maakaasun, lämmitysöljyn ja polttoöljyn tuotoista aikaväliltä 1994–2014, siltä osin kuin aineistoa on saatavilla. Likelihood ratio -testin avulla estimoidaan kaikille aikasarjoille regiimien määrä,jonka jälkeen Markov regiiminvaihtomallia hyödyntäen määritetään yksittäisten regiimientuottojakaumien ominaisuudet sekä regiimien välinen transitiomatriisi. Tulokset regiimien lukumäärän osalta osoittavat, että energiafutuurien päiväkohtaisten tuottojen aikasarjoissa regiimien lukumäärä vaihtelee kolmen ja kuuden välillä. Viikko- ja kuukausituottojen kohdalla kaikkien energiafutuurien prosesseissa regiimien lukumäärä on kaksi. Kun regiimejä on enemmän kuin kaksi, on prosessilla taipumus muodostaa regiimeistä koostuvia ryhmiä. Prosessi pysyy ryhmän sisällä yleensä pitkään, koska todennäköisyys siirtyä ryhmään kuuluvien regiimien välillä on suuri. Yksittäiset regiimit ryhmän sisällä eivät kuitenkaan ole kovin pysyviä. Näin ollen prosessi vaihtelee ryhmän sisäisten regiimien välillä tiuhaan. Regiimit, jotka eivät kuulu ryhmään, ovat yleensä pysyviä, mutta prosessi ajautuu niihin vain harvoin, sillä todennäköisyys siirtyä muista regiimeistä niihin on pieni. Tutkimuksen tulokset osoittavat myös, että prosesseissa, joita ohjaa kaksi regiimiä, nämä regiimit eivät välttämättä ole pysyvät bull- ja bear-markkinatilanteet. Tulokset osoittavat sen sijaan, että bear-markkinatilanne on energiafutuureissa selvästi vähemmän pysyvä.

Electrical Safety of Island Operated Low Voltage DC Network

Today, renewable energy technologies and modern power electronics have made it feasible to implement low voltage direct current (LVDC) microgrids (MGs) ca-pable to island operation. Such LVDC networks are particularly useful in remote areas. However, there are still pending issues in island operated LVDC MGs like electrical safety and controlled operation, which should be addressed before wide-scale implementation. This thesis is focused on the overall protection of an island operated LVDC network concept, including protection against electrical shocks, mains equipment protection and protection of photovoltaic (PV) power sources and battery energy storage systems (BESSs). The topic is approached through ex-amination of the safety hazards and the appropriate methods to protect against them, comprising considerations for earthing system selection and realisation of the protection system.

Observations of Acoustic Emission in Power Semiconductors

Industrial, electrical power generation, and transportation systems, to name but a few, rely heavily on power electronics to control and convert electrical power. Each of these systems, when encountering an unexpected failure, can cause significant financial losses, or even an emergency. A condition monitoring system would help to alleviate these concerns, but for the time being, there is no generally accepted and widely adopted method for power electronics. Acoustic emission is used as a failure precursor in many applications, but it has not been studied in power electronics so far. In this doctoral dissertation, observations of acoustic emission in power semiconductor components are presented. The acoustic emissions are caused by the switching operation and failure of power transistors. Three types of acoustic emission are observed. Furthermore, aspects related to the measurement and detection of acoustic phenomena are discussed. These include sensor performance and mechanical construction of experimental setups. The results presented in this dissertation are the outset of a research program where it will be determined whether an acoustic-emission-based condition monitoring method can be developed.

Design and Simulation of High-Speed Rotating Electrical Machinery

Global energy consumption has been increasing yearly and a big portion of it is used in rotating electrical machineries. It is clear that in these machines energy should be used efficiently. In this dissertation the aim is to improve the design process of high-speed electrical machines especially from the mechanical engineering perspective in order to achieve more reliable and efficient machines. The design process of high-speed machines is challenging due to high demands and several interactions between different engineering disciplines such as mechanical, electrical and energy engineering. A multidisciplinary design flow chart for a specific type of high-speed machine in which computer simulation is utilized is proposed. In addition to utilizing simulation parallel with the design process, two simulation studies are presented. The first is used to find the limits of two ball bearing models. The second is used to study the improvement of machine load capacity in a compressor application to exceed the limits of current machinery. The proposed flow chart and simulation studies show clearly that improvements in the high-speed machinery design process can be achieved. Engineers designing in high-speed machines can utilize the flow chart and simulation results as a guideline during the design phase to achieve more reliable and efficient machines that use energy efficiently in required different operation conditions.

Automated system of seedling image analysis (SVIS) and electrical conductivity to assess sun hemp seed vigor

The development of new procedures for quickly obtaining accurate information on the physiological potential of seed lots is essential for developing quality control programs for the seed industry. In this study, the effectiveness of an automated system of seedling image analysis (Seed Vigor Imaging System - SVIS) in determining the physiological potential of sun hemp seeds and its relationship with electrical conductivity tests, were evaluated. SVIS evaluations were performed three and four days after sowing and data on the vigor index and the length and uniformity of seedling growth were collected. The electrical conductivity test was made on 50 seed replicates placed in containers with 75 mL of deionised water at 25 ºC and readings were taken after 1, 2, 4, 8 and 16 hours of imbibition. Electrical conductivity measurements at 4 or 8 hours and the use of the SVIS on 3-day old seedlings can effectively detect differences in vigor between different sun hemp seed lots.

Ventricular rate during acute atrial fibrillation and outcome of electrical cardioversion: The FinCV Study

The impact of ventricular rate (VR) on the outcome of electrical cardioversion (ECV) of acute atrial fibrillation (AF) is currently unknown. We aimed to determine the effect of VR during acute AF on the success of ECV, recurrence of AF and occurrence of post-cardioversion complications in 30 days follow-up. All ECVs performed in patients with acute atrial fibrillation lasting <48 hours in 2 Finnish university hospitals during 2003-2010 and 1 central hospital during 2010 were retrospectively identified. A total of 6,624 ECVs were performed in 2,821 consecutive patients. VR≤60 BPM was defined low and VR≥160 BPM high. The median VR before ECV was 109 BPM. The success rate of ECV was 94.2%. Bradycardia occurred in 62 (0.9%) and thromboembolic complications in 39 (0.6%) ECVs. Low VR was observed before 75 (1.1%) ECVs and male sex was its only independent predictor. High VR was observed in 165 (2.5%) ECVs. The independent predictors of high VR were younger age, <12 h episode duration, no previous history of AF and alcohol abuse. Low or high VR were not related to the success of ECV, incidence of thromboembolic or bradycardic complications, or recurrence of AF, although VR was significantly (p<0.001) lower in the patients in whom AF recurred. In conclusion, ECV of acute AF is an effective procedure and VR during AF does not affect its efficacy, the maintenance of sinus rhythm or the incidence of bradycardic, thromboembolic or other complications during 30 days follow-up after ECV. Low VR is predominately observed in male patients, while high VR was a feature related to a shorter history of AF and high alcohol-intake.

Energy Efficiency in Electrical Drive Systems: Technical potentials, barriers and policy approaches for small and medium industries in Ghana

Today industries and commerce in Ghana are facing enormous energy challenge. The pressure is on for industries to reduce energy consumption, lower carbon emissions and provide se-cured power supply. Industrial electric motor energy efficiency improvement is one of the most important tools to reduce global warming threat and reduce electricity bills. In order to develop a strategic industrial energy efficiency policy, it is therefore necessary to study the barriers that inhibit the implementation of cost – effective energy efficiency measures and the driving forces that promote the implementation. The aim of this thesis is to analyse the energy consumption pattern of electric motors, study factors that promote or inhibit energy efficiency improvements in EMDS and provide cost – effective solutions that improve energy efficiency to bridge the existing energy efficiency gap in the surveyed industries. The results from this thesis has revealed that, the existence of low energy efficiency in motor-driven systems in the surveyed industries were due to poor maintenance practices, absence of standards, power quality issues, lack of access to capital and limited awareness to the im-portance of energy efficiency improvements in EMDS. However, based on the results pre-sented in this thesis, a policy approach towards industrial SMEs should primarily include dis-counted or free energy audit in providing the industries with the necessary information on potential energy efficiency measures, practice best motor management programmes and estab-lish a minimum energy performance standard (MEPS) for motors imported into the country. The thesis has also shown that education and capacity development programmes, financial incentives and system optimization are effective means to promote energy efficiency in elec-tric motor – driven systems in industrial SMEs in Ghana