Comparison of cardiovascular responses between remifentanil and fentanyl on laryngoscopy and tracheal intubation in patients undergoing elective surgery.

This was a prospective, randomized, double-blind study comparing the effect of remifentanil and fentanyl on cardiovascular responses from laryngoscopy and tracheal intubation. Forty-four ASA I or II patients aged between 18-65 yrs scheduled for elective surgery under general anaesthesia, were recruited and randomized into two groups. Each patient in Group R received remifentanil of 0.5 mcg/kg bolus over 30 seconds followed by an infusion of 0.25 mcg/kg/min and each patient in Group F received fentanyl of 2 mcg/kg bolus over 30 seconds followed by an infusion of normal saline. Anaesthesia was then induced with propofol, rocuronium and 2% sevoflurane with 100% oxygen. Cardiovascular changes were recorded every minute for 3 minutes after induction and 5 minutes after tracheal intubation. The heart rate remained stable throughout the induction and intubation period in both groups. None of the patients in the remifentanil group develop bradycardia. Systolic blood pressure (SBP) and mean arterial pressure (MAP) were significantly lower in the fentanyl group at the 3rd minute post-induction and 5th minute post-intubation (p < 0.05). Diastolic blood pressure (DBP) in the fentanyl group was significantly lower at the 2nd and 3rd minute post-induction and 4th and 5th minute post-intubation (p < 0.05). The blood pressure remained stable for the remifentanil group throughout the induction and intubation period. Six patients (27.2%) in the fentanyl group and one patient (4.5%) in the remifentanil group experienced hypertension. Three patients (13.7%) from each group experienced hypotensive episodes. In conclusion, remifentanil 0.5 mcg/kg bolus followed by 0.25 mcg/kg/min infusion resulted in SBP, MAP and DBP remained slightly lower than baseline throughout the whole period but still consider stable, as these changes were not statistically significant

Indirect sliding mode control of power converters via double integral sliding surface

Author name used in this publication: Chi K. Tse2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

An evaluation of the practicality of sliding mode controllers in DC-DC converters and their general design issues

Author name used in this publication: Chi K. TseRefereed conference paper2005-2006 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

A family of PWM based sliding mode voltage controllers for basic DC-DC converters

Author name used in this publication: Chi K. TseRefereed conference paper2005-2006 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Implementation of pulse-width-modulation based sliding mode controller for boost converters

Author name used in this publication: Chi K. Tse2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

General design issues of sliding-mode controllers in DC-DC converters

Author name used in this publication: Chi K. Tse2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

An analog implementation of pulse-width-modulation based sliding mode controller for dc-dc boost converters

Author name used in this publication: Chi K. TseRefereed conference paper2006-2007 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

A unified approach to the design of PWM-based sliding-mode voltage controllers for basic DC-DC converters in continuous conduction mode

Author name used in this publication: Chi K. Tse2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Characterization of volatile organic compounds at a roadside environment in Hong Kong: An investigation of influences after air pollution control strategies

Vehicular emission is one of the important anthropogenic pollution sources for volatile organic compounds (VOCs). Four characterization campaigns were conducted at a representative urban roadside environment in Hong Kong between May 2011 and February 2012. Carbon monoxide (CO) and VOCs including methane (CH4), non-methane hydrocarbons (NMHCs), halocarbons, and alkyl nitrates were quantified. Both mixing ratios and compositions of the target VOCs show ignorable seasonal variations. Except CO, liquefied petroleum gas (LPG) tracers of propane, i-butane and n-butane are the three most abundant VOCs, which increased significantly as compared with the data measured at the same location in 2003. Meanwhile, the mixing ratios of diesel- and gasoline tracers such as ethyne, alkenes, aromatics, halogenated, and nitrated hydrocarbons decreased by at least of 37%. The application of advanced multivariate receptor modeling technique of positive matrix factorization (PMF) evidenced that the LPG fuel consumption is the largest pollution source, accounting for 60 ± 5% of the total quantified VOCs at the roadside location. The sum of ozone formation potential (OFP) for the target VOCs was 300.9 μg-O3 m-3, which was 47% lower than the value of 567.3 μg-O3 m-3 measured in 2003. The utilization of LPG as fuel in public transport (i.e., taxis and mini-buses) contributed 51% of the sum of OFP, significantly higher than the contributions from gasoline- (16%) and diesel-fueled (12%) engine emissions. Our results demonstrated the effectiveness of the switch from diesel to LPG-fueled engine for taxis and mini-buses implemented by the Hong Kong Special Administrative Region (HKSAR) Government between the recent ten years, in additional to the execution of substitution to LPG-fueled engine and restrictions of the vehicular emissions in compliance with the updated European emission standards

On the color stability of phosphor-converted white LEDs under DC, PWM, and bilevel drive

Most commercial white LEDs are made from nitride-based blue LEDs coated with yttrium aluminium garnet phosphor, which produce spectra that shift in opposite directions under the influences of drive current and junction temperature changes. This property gives rise to different emitted spectra, hence chromaticity properties, when the LED is driven/dimmed by different current waveforms. By using a commercial white LED sample, LUXEON K2, the effects of drive current and junction temperature on the changes of chromaticity coordinates are studied experimentally. The impact of dc, pulse width modulation (PWM), and bilevel current waveform is discussed through a graphical analysis, followed by experimental verification. It is proven that dc offers the best color stability over dimming due to the counteracting influences of drive current and junction temperature variations, whereas an LED constantly suffers from noneliminable chromaticity changes when driven by the PWM. Theoretical explanations are given to justify these cases, and it is found that, for the case of dc drive, an ideal heat sinks thermal resistance can be selected based on a simple equation to minimize the overall chromaticity change over dimming. This paper provides an in-depth discussion on the relations between the chromaticity properties of phosphor-converted (pc) white LEDs and the driving/dimming methods used. © 2011 IEEE.published_or_final_versio