Krishnan Muralikrishnan

Stanley Medical College, Chennai, Tamil Nādu, India

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Publications (7)1.52 Total impact

  • D V Ghodke, K Muralikrishnan, Bijendra Singh
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    ABSTRACT: A novel multiplexed scheme is demonstrated to combine two or more pulsed solid state pulsers of moderate capabilities. Pulse power supply comprising of two solid state pulsers of ∼6 kW rating each in multiplexed mode with common magnetic pulse compression stage was demonstrated and optimized for operating with a wide aperture kinetically enhanced copper vapor laser. Using this new configuration, the multiplexed pulsed power supply was capable of operating efficiently at net repetition-rate of ∼13 kHz, 12 kW (wall plug average power), 18-20 kV discharge voltage and pulse rise-time of ∼80 ns. The laser under multiplexed configuration delivered un-interrupted output power of about ∼80 W with scope of further increase in laser output power in excess of 100 W.
    The Review of scientific instruments 11/2013; 84(11):113102. · 1.52 Impact Factor
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    ABSTRACT: Beneficial effects of Yoga have been postulated to be due to modulation of the autonomic nervous system. To assess the effect of Isha Yoga practices on cardiovascular autonomic nervous system through short-term heart rate variability (HRV). Short-term HRV of long-term regular healthy 14 (12 males and 2 females) Isha Yoga practitioners was compared with that of age- and gender-matched 14 (12 males and 2 females) non-Yoga practitioners. ECG Lead II and respiratory movements were recorded in both groups using Polyrite during supine rest for 5 min and controlled deep breathing for 1 minute. Frequency domain analysis [RR interval is the mean of distance between subsequent R wave peaks in ECG], low frequency (LF) power, high frequency (HF) power, LF normalized units (nu), HF nu, LF/HF ratio] and time domain analysis [Standard Deviation of normal to normal interval (SDNN), square of mean squared difference of successive normal to normal intervals (RMSSD), normal to normal intervals which are differing by 50 ms (NN50), and percentage of NN50 (pNN50)] of HRV variables were analyzed for supine rest. Time domain analysis was recorded for deep breathing. Results showed statistically significant differences between Isha Yoga practitioners and controls in both frequency and time domain analyses of HRV indices, with no difference in resting heart rate between the groups. Practitioners of Isha Yoga showed well-balanced beneficial activity of vagal efferents, an overall increased HRV, and sympathovagal balance, compared to non-Yoga practitioners during supine rest and deep breathing.
    Journal of Ayurveda and integrative medicine 04/2012; 3(2):91-6.
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    ABSTRACT: Hypertension (HT) is a major silent disease affecting young people because of their hereditary and modern lifestyles. Target organ damages occur before overt hypertension is diagnosed. Many offspring of HT parents show early changes in their cardiovascular autonomic functions. Heart rate variability (HRV) provides a window to understand the cardiac autonomic balance. This study was designed to quantify and to compare the HRV among the normotensive young male offspring without history of parenteral hypertension & diabetic (control group, n = 25, age 20.8 +/- 2.4, BMI 24.4 +/- 3.1) with parenteral history of hypertension & non diabetic (study group n = 25, age 19.7 +/- 1.9, 24.05 +/- 3.5). Blood pressure, heart rate (HR), indices of short term HRV during supine rest and quiet standing, HR variation during timed controlled deep breathing was compared between the two groups. There were significant difference in low frequency (LF) power, HF power, total power. LF and HF expressed also in normalized units at rest and standing. In time domain standard deviation of normal to normal RR interval (SDNN) at supine rest and standing were significant. Respiratory sinus arrthymia (RSA), HF in normalized units, deep breathing difference (BDD) and the ratio of maximum RR to minimum RR were also significant in the control group than study group. In the present study there was an increased sympathetic and decreased parasympathetic activity in the study group. These findings are an early marker of cardiovascular autonomic impairment in subjects with parenteral history of hypertension.
    Indian journal of physiology and pharmacology 01/2011; 55(3):253-61.
  • M. Ramalatha, A.P. Karthick, S. Karthick, K. Muralikrishnan
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    ABSTRACT: The parameters like speed and resolution of an analog to digital converter (ADC) characterizes the performance of any control system in the real world. Among available ADC architectures flash, pipeline, sigma-delta and successive approximation register (SAR) have been frequently used to satisfy different requirements like speed, resolution and power. A flash architecture is conceptually the simplest and the easiest to design, but requires a large number of transistors and significant power because, an n-bit ADC requires 2n-1 comparators (one comparator for each threshold), which also present a significant capacitive load to the circuitry driving the ADC. Though flash ADC is preferred for its high speed, this speed decreases with increase in resolution. In order to achieve higher resolution, SAR ADC is preferred, but the speed of the ADC is very limited. Therefore for better trade-off between resolution and speed, the pipeline architecture is used. The concurrent operation of the pipelined stages is responsible for its increased efficiency. Each stage processes a new sample as soon as its residue is sampled by the following stage, which leads to a high throughput of one sample per clock cycle. The pipeline ADC is constructed by using switched capacitor (SC) circuit, which exploits the charge storing abilities of CMOS to achieve precision signal processing and is preferred in mixed-signal, A/D interfaces. A fat tree encoder (FTE) used in Flash ADC of each pipeline stage improves speed, reduces the latency, power consumption and area.
    Advances in Computational Tools for Engineering Applications, 2009. ACTEA '09. International Conference on; 08/2009
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    D.V. Ghodke, K. Muralikrishnan
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    ABSTRACT: This paper presents a zero voltage and zero current switching (ZVZCS), dual, two-transistor forward converter (DTTFC) for high input voltage and high power application. Two identical two-transistor forward converters (TTFC) are connected in series and coupled through a single transformer using two primary windings, because of which it operates like a full bridge and makes it suitable for high power application. It imposes only half the input voltage across each of the four switches. This DTTFC has advantage of high reliability as compared to the full or half bridge converters. A modified pulse width modulation (PWM) controller is proposed for DTTFC to minimize the circulating RMS current flowing through the transformer and switching devices. This is without any extra hardware in series with primary of the transformer or in secondary. Conduction losses, being proportional to the square of the conducting current in a transformer and MOSFET, are important in high power converters operating at high currents. Since switching losses are also important in high frequency switching application, in DTTFC two switches, out of four switches, are turned-on and off at zero voltage condition due to the current in leakage inductance of a transformer. The remaining two switches are turned-off at zero voltage and turned-on at zero current condition due to transformer leakage inductance and minimized circulating current, over a wide range of load current. The advantages of this simple circuit topology is high efficiency, high reliability, low component count, and low cost, makes the new converter attractive for high input voltage, high power applications. In this paper we discuss the operating states, switching transitions, method of control, experimental results and associated waveforms of a MOSFET based practical 60 V, 50 A, 100 kHz, dual, two-transistor forward DC-DC converter operating at 750 V input bus. The measured efficiency was 95.07% at full load with maximum efficiency of 96.6% at 70% load
    Power Electronics Specialists Conference, 2002. pesc 02. 2002 IEEE 33rd Annual; 02/2002
  • D.V. Ghodke, K. Muralikrishnan
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    ABSTRACT: This paper presents a soft switching two transistor forward converter with a clamping circuit connected in the primary side of the transformer. This clamping circuit will reduce the reverse recovery effects of the output rectifying diodes, increasing the overall efficiency. Moreover the switching devices are turned-on with zero current switching (ZCS) and turned-off with zero voltage switching (ZVS), further increasing efficiency and reducing EMI, and so are suitable for kW power range application. Theoretical analyses of the converter along with experimental results for a 150 V, 10 A, 100 kHz experimental prototype is presented.
    Power Electronics Specialists Conference, 2002. pesc 02. 2002 IEEE 33rd Annual; 02/2002
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    ABSTRACT: Obesity has been shown to affect cardiovascular function. Heart rate variability (HRV) has been an accepted method of measuring cardiovascular autonomic function. The aim of the study is to evaluate the impact of obesity on HRV using Poincaré plot (POP) analysis. A finding of sympathovagal imbalance in pre-obese adults in respiratory sinus arrhythmia (RSA) could provide important diagnostic information about early subclinical autonomic dysfunction in obesity. Thirty one obese (BMI 26.84 +/- 2.47) adult males (25.42 +/- 7.86 years) were compared with 31 normal subjects (25.38 +/- 4.61 years). In all participants, anthropometric and blood pressure (BP) measurements were performed. After rest at supine position for 5 minutes, they were asked to do control deep breathing for 1 minute. HRV was measured in terms of POP analysis. Differences in Resting heart rate (RHR) (P < or = 0.025), Pulse pressure (PP) (P < or = 0.048), SD1 (P < or = 0.042) and SD2 (P < or = 0.039) of the POP between the two groups were significant. Correlation between Body mass index (BMI) and (PP) (p = 0.19); SD1 (p = 0.47) and SD2 (p = 0.39) of the POP were significant in obese groups. Obesity is related to sympathovagal imbalance characterized by depressed parasympathetic tone and increased sympathetic activity. Nonlinear methods like POP permit simple assessment of autonomic function, despite measuring different aspects of HRV.
    Indian journal of physiology and pharmacology 57(1):31-7.

Publication Stats

29 Citations
1.52 Total Impact Points

Institutions

  • 2011–2012
    • Stanley Medical College
      Chennai, Tamil Nādu, India
  • 2009
    • Karpaga Vinayaga College of Engineering and Technology
      Chennai, Tamil Nādu, India
  • 2002
    • Raja Ramanna Centre for Advanced Technology
      Indaur, Madhya Pradesh, India