Naveed Ashraf - Academia.edu (original) (raw)
Papers by Naveed Ashraf
Applied Sciences
Single-phase AC–AC converters with a direct power conversion approach are receiving rapid develop... more Single-phase AC–AC converters with a direct power conversion approach are receiving rapid development as they have the ability to produce the regulated non-inverting and inverting form of the input voltage at the output. This feature enables them to correct the line voltage profile once they are used as dynamic voltage restorers if there is an issue of voltage sag or swell in the power distribution system. The regulated non-inverting and inverting form of the output voltage may also be used to obtain the step change in the output frequency, as it is required in many industrial drive systems. However, the realization of such existing circuits needs a large number of components and semiconductor devices, especially switching transistors. The operating control (on and off) of the transistors is directly associated with the use of gate control circuits. The count of such circuits is critical as their volume and cost are much greater than the operating transistors. The number of conducti...
Applied Sciences, 2021
The problem of voltage sag and swell is one of the major reasons for low-quality power in the dis... more The problem of voltage sag and swell is one of the major reasons for low-quality power in the distribution system. Normally, it results from the system’s faults, including line-to-ground and line-to-line, non-linear characteristics of loads and sources. Its effect is very serious for the critical loads as their performance is very sensitive to the variation in voltage. The stabilization of voltage is a mandatory requirement in such a situation. The correction of such problems requires the addition and subtraction of the voltage once the line voltage is decreased and increased. This behavior of the correcting voltage is ensured by the use of voltage controllers that can convert a constant input voltage into a non-inverted and inverted variable form. Their voltage gains depend on the depth level of the problem. The voltage buck and boost capabilities of the AC voltage stabilizers can tackle the problems having any depth level. The smartness of such a system depends on the number of el...
Applied Sciences, 2021
In numerous applications, such as the correction of grid voltage during voltage sag or swell even... more In numerous applications, such as the correction of grid voltage during voltage sag or swell events caused by system faults, it is necessary to ensure the stabilization of the output voltage with in-phase and out-phase features. This feature can also be employed in high-voltage-gain AC to DC conversion. AC voltage control schemes with one-stage conversion are viable approaches in this regard as only voltage regulation is needed. This conversion approach has strong potential for such applications as it is simple to realize. The voltage-correcting compensators are connected in series with the lines. The inputs of the AC voltage controllers employed in the voltage-correcting compensators may be connected to the faulty phase or other healthy phases. The number of AC voltage controllers used in a voltage compensator are one and two if its input power is drawn from the faulty and non-faulty phases, respectively. In the latter case, voltage gains and phase adjustment are major problems. Th...
Applied Sciences, 2021
The induction heating process at a domestic level is getting attention nowadays as this power con... more The induction heating process at a domestic level is getting attention nowadays as this power converting topology ensures clean, reliable, flexible, and fast operation. The low input frequency is converted to required regulated high output frequency with indirect and direct power converting approaches. The circuit and control complexity and high conversion losses associated with indirect power converting approaches lower their uses for domestic induction systems. The direct ac-ac power conversion approach is one of the viable solutions for low and medium power level loads, especially for domestic induction heating loads. The circuit complexity, cost, and conversion losses of the direct power converting systems depend on the number of the controlled switching devices as each controlled switch requires one gate driving circuit and one isolated dc supply. Simplified pulse width modulation (PWM) switching control also lower their control effort. Therefore, in this article, a simplified ...
Electronics, 2020
Induction heating (IH) is an environmentally friendly solution for heating and melting processes.... more Induction heating (IH) is an environmentally friendly solution for heating and melting processes. The required high-frequency magnetic field is accomplished through frequency controllers. Direct frequency controllers (DFC) are preferred to dual converters as they have low conversion losses, compact size, and simple circuit arrangement due to low component count. Numerous frequency controllers with complex switching algorithms are employed in the induction heating process. They have a complicated circuit arrangement, and complex control as their switching sequences have to synchronize with source voltage that requires the zero-crossing detection of the input voltage. They also have a shoot-through problem and poor power quality. Therefore, this research proposes a novel frequency controller with a low count of six controlled switching devices without a zero-crossing detector (ZCD) having a simple control arrangement. The required switching signals are simply generated by using any pu...
Mathematical Problems in Engineering, 2019
The suggested single-phase ac-to-ac matrix converter operated with inverting and noninverting cha... more The suggested single-phase ac-to-ac matrix converter operated with inverting and noninverting characteristics may solve the grid voltage swell and sag problem in power distribution system, respectively. It is also employed as a direct frequency changer for domestic induction heating. The output voltage is regulated through duty cycle control of high frequency direct PWM (DPWM) and indirect PWM (IDPWM) switching devices. The DPWM control switches control the switching states of IDPWM switching devices. The inverting and noninverting characteristics are achieved with low voltage stresses and hence low dv/dt across the high and low frequency-controlled switches. This reduces their voltage rating and losses. The high voltage overshoot problem in frequency step-up operation is also analyzed. The sliding mode (SM) controller is employed to solve this problem. Pulse selective approach determines the power quality of load voltage. The validity of the mathematically computed values is carrie...
Applied Sciences
Single-phase direct frequency converters are gaining attraction at the research and academic leve... more Single-phase direct frequency converters are gaining attraction at the research and academic level as they are rapidly getting space over conventional multistage converters. The converters developed with a rectification and inversion process using a DC-link level are examples of multistage converters with some serious concerns such as an increase in the overall weight, losses, and cost. They also suffer from the low-reliability issue due to the issues involved with DC-link capacitors and problems linked with electromagnetic interference (EMI) caused by high-frequency pulse width modulation (PWM) switching. These problems are addressed with line frequency switching cycloconverters. In these converters, the power quality of the output voltage is improved by governing the amplitude of some selected output pulses or half-cycles. For this purpose, a low-frequency multiple tapping transformer may be used to obtain various voltage levels. However, its use is the main source of increased ov...
Pakistan Journal Of Neurological Surgery, 2020
Background & Objectives: Severe traumatic brain injury is one of the leading causes of mortality ... more Background & Objectives: Severe traumatic brain injury is one of the leading causes of mortality and morbidity.Efficient management of severe traumatic brain injury demands a specialty driven focused intensive care. We developed our model of closed ICU driven by Neurosurgical Neurointensivist and the corollary to thiscommitment is a TBI patient centered Neurocritical care with the capacity and capability to deal with most of the neurological illnesses.Materials & Methods: A prospective study was conducted to find out the impact of the establishment of closed system of neurocritical care on 5 year mortality of severe TBI. Total 1288 patients met the inclusion criteria, which were enrolled. Tabulation was done for gender, age range, Glasgow outcome scale and mortality.Results: It was observed that mortality reduced from 47% to 35% over a span of five years. The most common age range was 30-40 years, which is the most productive group of any population. Bed sore incidence is always on ...
Energies, 2022
Variable voltage and frequency are required to govern the torque-speed characteristics of many in... more Variable voltage and frequency are required to govern the torque-speed characteristics of many industrial drive systems. Traditionally, this is achieved with a power converting system implemented with multistage converters. This technology is based on rectifying AC power into DC and then DC into AC with an inverter circuit. The power quality concerns of both conversion stages are tackled by selecting high switching frequency PWM control and harmonics mitigation filters. Also, using a bulky DC-link capacitor is one of the big sources of low system reliability, so this approach increases the conversion losses, circuit, and control complications. The frequency step-down conversion is very attractive with direct AC-AC converters as it has a simple control and circuit structure, but these converters face poor power quality challenges once the output frequency is decreased with respect to an input. In these converters, the total harmonic distortion (THD) of the output voltage becomes very...
Surgical Neurology International, 2021
Background: Pediatric anemia has a high prevalence in developing countries such as Pakistan. It i... more Background: Pediatric anemia has a high prevalence in developing countries such as Pakistan. It is common knowledge among hospital specialties but little is done to manage this condition by hospitalists. The issue is compounded with a poor primary care infrastructure nationally. The aim of this study is to bring to light the high prevalence of anemic children in neurosurgery and to describe the difficulties in managing their anemia in a tertiary hospital setting. A literature review is presented highlighting the socioeconomic difficulties that contribute to this widespread comorbidity and the difficulty in managing it from a hospital specialty point of view. Methods: A prospective descriptive case series was carried out between March 2020 and September 2020. All patients under the age of 13 who presented to our department for traumatic brain injury (TBI) meeting our inclusion and exclusion criteria were enrolled and assessed for the presence and severity of anemia. Demographic data ...
Background: Backache is second most common problem presenting to the primary healthcare providers... more Background: Backache is second most common problem presenting to the primary healthcare providers. Lumbar discectomy has been revolutionized from open conventional discectomy to endoscopic removal. Endoscopic procedures are proving their superiority regarding good outcome, less wound site pain and shorter hospital stay, in Neurosurgery as well. Micro discectomy and Endoscopic discectomy is used only in few centres in Pakistan. This study aimed to share our experience of early surgical outcome endoscopic lumbar discectomy in terms postoperative pain improvement and duration of hospital stay Methods: This prospective study was carried out at Neurosurgery Department, Jinnah Hospital, Lahore from Jan 2014 to Jan 2016. During this period, 35 patients of both sexes, aging between 20 and 60 years, with symptoms and signs of lumbago with sciatica were enrolled. Data was collected on a questionnaire after informed verbal and written consent. Results: A total of 35 patients were operated incl...
Applied Sciences, 2021
Single-phase and three-phase AC-AC converters are employed in variable speed drive, induction hea... more Single-phase and three-phase AC-AC converters are employed in variable speed drive, induction heating systems, and grid voltage compensation. They are direct frequency and voltage controllers having no intermediate power conversion stage. The frequency controllers govern the output frequency (low or high) in discrete steps as per the requirements. The voltage controllers only regulate the RMS value of the output voltage. The output voltage regulation is achieved on the basis of the various voltage control techniques such as phase-angle, on-off cycle, and pulse-width modulation (PWM) control. The power quality of the output voltage is directly linked with its control techniques. Voltage controllers implemented with a simple control technique have large harmonics in their output voltage. Different control techniques have various harmonics profiles in the spectrum of the output voltage. Traditionally, the evaluation of power quality concerns is based on the simulation platform. The val...
Applied Sciences, 2021
The attractive features of the direct AC-AC converters increase their use in many applications su... more The attractive features of the direct AC-AC converters increase their use in many applications such as voltage control for a heavy-duty load that has a high time constant, AC machine drives, and heating systems based on the induction process. These converters process power in single-stage having simple circuit topologies with reduced switching devices and circuit components. These characteristics lead to the efficient power conversion process. The use of a low-frequency input transformer with multiple output tapping for the regulation of output voltage and frequency is one of the major sources of cost, size, and conversion losses. The complication in the switching algorithms is also the main concern in these converters. The preceding deficiencies lower their potency to be used in daily life. The costly controllers or processors are to be employed to realize the complex control techniques or algorithms. That increases the overall cost and circuit complication. This paper introduces t...
Journal of the Pakistan Medical Association, 2020
Objective: To identify the deficiencies in patient note record-taking with the aim of improving t... more Objective: To identify the deficiencies in patient note record-taking with the aim of improving the quality to meet international standards. Methods: The prospective clinical quality improvement audit study was conducted at the department of Neurosurgery, Allama Iqbal Medical College, Jinnah Hospital Lahore from January 219 to February 2020. The first audit cycle was carried out in July 2019, after data anonymisation, the notes from 1st January to 31st June were analysed in the first audit cycle against a hybrid proforma containing entries deemed essential in operative notes according to the guidelines of the Royal College of Surgeons of England. The guidelines were subsequently disseminated among postgraduate trainees using various methods. Post-intervention, randomly selected patient-notes from 1st August to 31st December 2019 were analysed in the second audit which was done in February 2020. The result of the two audits were compared to assess significance of association between ...
Surgical Neurology International, 2020
Background: Intraoperative imaging addresses the limitations of frameless neuronavigation systems... more Background: Intraoperative imaging addresses the limitations of frameless neuronavigation systems by providing real-time image updates. With the advent of new multidetector intraoperative computed tomography (CT), soft tissue can be visualized far better than before. We report the early departmental experience of our intraoperative CT scanner’s use in a wide range of technically challenging neurosurgical cases. Methods: We retrospectively analyzed the data of all patients in whom intraoperative CT scanner was utilized. Out of 31 patients, 24 (77.4%) were cranial and 8 (22.6%) spinal cases. There were 13 male (41.9%) and 18 (58.1%) female patients, age ranged from 1 to 83 years with a mean age of 34.29 years ±17.54 years. Seven patients underwent spinal surgery, 2 cases were of orbital tumors, and 16 intra-axial brain tumors, including 5 low- grade gliomas, 10 high-grade gliomas, and 1 colloid cyst. There were four sellar lesions and two multiloculated hydrocephalus. Results: The int...
Pakistan Journal Of Neurological Surgery, 2019
Objectives: To highlight the role of public sector hospitals in sharing the major burden of sever... more Objectives: To highlight the role of public sector hospitals in sharing the major burden of severely head injured patients in a resource constrained economically striving countryMaterials and Methods: The study was conducted in the Neurosurgery department of Jinnah Hospital, Lahore, Pakistan. 70 patients with moderate to severe TBI cases above one year of age were included. The data was analyzed for the cost estimation for the period of six months, for the following heads: 1) hospital cost per day, 2) ICU setup cost per day, and 3) salaries of hospital staff per day.Results: There were 53 cases of moderate injury and 17 cases of severe injury. Mean hospital stay was 14 days, minimum number of stay was 2 days and the maximum number of stay was 124 days in six months. Overall, in six months, per day cost of hospital bills head was Rs. 42,333/$ 263/€ 238. For the ICU setup head, the total cost was Rs. 17,9923/$1130/€ 1016 per day. The salary head’s total cost was Rs. 2573/$16.06/€ 14.4...
Pakistan Journal Of Neurological Surgery, 2019
Objective: We evaluated the frequency of post traumatic amnesia (PTA) in close mild traumatic bra... more Objective: We evaluated the frequency of post traumatic amnesia (PTA) in close mild traumatic brain injury (TBI) via. Galveston Orientation and Amnesia Test (GOAT).Materials & Methods: A total of 115 patients with mild TBI, both male and female, aged between 14 to 60 years and presenting within the first 6 hours were included. Assessment with the GOAT was performed within 6 hours of admission. Post traumatic amnesia was recorded.Results: Patients’ mean age was 39.21 years. Majority of the patients (64.34%) were between 36- 60 years of age. Prevalence of post traumatic amnesia (PTA) in closed mild TBI was found in 27.83% patients, whereas, there was no post traumatic amnesia in 72.17% patients. Mean admission GCS was 14.54 and the mean GOAT score was 83.89 in all patients GCS 14/15. There was more prevalence of PTA in age 36-60 years, in male patients and “time since injury” in >3 hours. Mean GOAT was 68.3 in patients (30.19%) with PTA with GCS 14, whereas, mean GOAT was 74.8 in p...
Energies, 2019
In this research, a new single-phase direct AC-to-AC converter, operating in buck and boost mode,... more In this research, a new single-phase direct AC-to-AC converter, operating in buck and boost mode, with a bipolar voltage gain, is proposed. The operation is accomplished through high frequency direct and indirect PWM control of a single switch with low voltage stresses. This reduces, not only the control effort, but also the switching losses. The low voltage stresses across the high frequency switches, reduce the dv/dt problem significantly without any loss and bulky voltage snubber arrangement. The operation, in its all-operating modes, has a low inductor ripple current and switching current. The proposed converter may be employed as an AC voltage restorer in a power distribution system to cope with the voltage sag and swell issues. The detailed analysis of the proposed converter is carried out in order to compare its performance with the existing converters. The simulation results obtained using the MATLAB/Simulink environment are verified through experimental results.
Journal of neurological surgery. Part A, Central European neurosurgery, Jan 18, 2018
The use of single/dual external ventricular drains (EVD) for reducing intraventricular hemorrhag... more The use of single/dual external ventricular drains (EVD) for reducing intraventricular hemorrhage (IVH) is under investigation. A randomized controlled trial was conducted to compare postoperative reduction of IVH volume using single- and dual-catheter drainage in spontaneous IVH patients. We investigated factors that may influence an effective hematoma volume reduction by EVDs. The average cerebrospinal fluid (CSF) drainage volumes were analyzed. Computed tomography (CT) scans were performed on admission, 24 hours and 48 hours after EVD placement, and then on days 5 and 8. Patient group 1 was treated with a single EVD; patient group 2 was treated with bilateral EVDs. The IVH volume was calculated in all ventricles. A multivariate analysis was conducted to investigate variables that can influence the extent of hematoma volume reduction with a bilateral EVD. Regression followed by a Pearson correlation was performed to observe the strength of association of cofounders with the IVH ...
2017 International Conference on Electrical Engineering (ICEE), 2017
The controlled ac-to-dc converters are used to control the output dc voltage. A six pulses contro... more The controlled ac-to-dc converters are used to control the output dc voltage. A six pulses controlled ac-to-dc converter is one of the efficient converters that is widely used in many industrial applications. The main advantage of any higher pulse converter in ac-to-dc conversion is low ripple factor but on the other hand, it highly distorts the input supplied currents. This distortion degrades the power factor, and increases the stresses across the protective devices and measuring units in the power system, hence exhibits poor power quality. It becomes important to analyze the power quality in ac-to-dc power conversion. A new approach called pulse selective method is introduced to analytically calculate the harmonics in a three phase rectifier circuit both for input and output. Then power quality performance parameters are analyzed on the basis of computed harmonics. Simulation modeling is used to verify the proposed method.
Applied Sciences
Single-phase AC–AC converters with a direct power conversion approach are receiving rapid develop... more Single-phase AC–AC converters with a direct power conversion approach are receiving rapid development as they have the ability to produce the regulated non-inverting and inverting form of the input voltage at the output. This feature enables them to correct the line voltage profile once they are used as dynamic voltage restorers if there is an issue of voltage sag or swell in the power distribution system. The regulated non-inverting and inverting form of the output voltage may also be used to obtain the step change in the output frequency, as it is required in many industrial drive systems. However, the realization of such existing circuits needs a large number of components and semiconductor devices, especially switching transistors. The operating control (on and off) of the transistors is directly associated with the use of gate control circuits. The count of such circuits is critical as their volume and cost are much greater than the operating transistors. The number of conducti...
Applied Sciences, 2021
The problem of voltage sag and swell is one of the major reasons for low-quality power in the dis... more The problem of voltage sag and swell is one of the major reasons for low-quality power in the distribution system. Normally, it results from the system’s faults, including line-to-ground and line-to-line, non-linear characteristics of loads and sources. Its effect is very serious for the critical loads as their performance is very sensitive to the variation in voltage. The stabilization of voltage is a mandatory requirement in such a situation. The correction of such problems requires the addition and subtraction of the voltage once the line voltage is decreased and increased. This behavior of the correcting voltage is ensured by the use of voltage controllers that can convert a constant input voltage into a non-inverted and inverted variable form. Their voltage gains depend on the depth level of the problem. The voltage buck and boost capabilities of the AC voltage stabilizers can tackle the problems having any depth level. The smartness of such a system depends on the number of el...
Applied Sciences, 2021
In numerous applications, such as the correction of grid voltage during voltage sag or swell even... more In numerous applications, such as the correction of grid voltage during voltage sag or swell events caused by system faults, it is necessary to ensure the stabilization of the output voltage with in-phase and out-phase features. This feature can also be employed in high-voltage-gain AC to DC conversion. AC voltage control schemes with one-stage conversion are viable approaches in this regard as only voltage regulation is needed. This conversion approach has strong potential for such applications as it is simple to realize. The voltage-correcting compensators are connected in series with the lines. The inputs of the AC voltage controllers employed in the voltage-correcting compensators may be connected to the faulty phase or other healthy phases. The number of AC voltage controllers used in a voltage compensator are one and two if its input power is drawn from the faulty and non-faulty phases, respectively. In the latter case, voltage gains and phase adjustment are major problems. Th...
Applied Sciences, 2021
The induction heating process at a domestic level is getting attention nowadays as this power con... more The induction heating process at a domestic level is getting attention nowadays as this power converting topology ensures clean, reliable, flexible, and fast operation. The low input frequency is converted to required regulated high output frequency with indirect and direct power converting approaches. The circuit and control complexity and high conversion losses associated with indirect power converting approaches lower their uses for domestic induction systems. The direct ac-ac power conversion approach is one of the viable solutions for low and medium power level loads, especially for domestic induction heating loads. The circuit complexity, cost, and conversion losses of the direct power converting systems depend on the number of the controlled switching devices as each controlled switch requires one gate driving circuit and one isolated dc supply. Simplified pulse width modulation (PWM) switching control also lower their control effort. Therefore, in this article, a simplified ...
Electronics, 2020
Induction heating (IH) is an environmentally friendly solution for heating and melting processes.... more Induction heating (IH) is an environmentally friendly solution for heating and melting processes. The required high-frequency magnetic field is accomplished through frequency controllers. Direct frequency controllers (DFC) are preferred to dual converters as they have low conversion losses, compact size, and simple circuit arrangement due to low component count. Numerous frequency controllers with complex switching algorithms are employed in the induction heating process. They have a complicated circuit arrangement, and complex control as their switching sequences have to synchronize with source voltage that requires the zero-crossing detection of the input voltage. They also have a shoot-through problem and poor power quality. Therefore, this research proposes a novel frequency controller with a low count of six controlled switching devices without a zero-crossing detector (ZCD) having a simple control arrangement. The required switching signals are simply generated by using any pu...
Mathematical Problems in Engineering, 2019
The suggested single-phase ac-to-ac matrix converter operated with inverting and noninverting cha... more The suggested single-phase ac-to-ac matrix converter operated with inverting and noninverting characteristics may solve the grid voltage swell and sag problem in power distribution system, respectively. It is also employed as a direct frequency changer for domestic induction heating. The output voltage is regulated through duty cycle control of high frequency direct PWM (DPWM) and indirect PWM (IDPWM) switching devices. The DPWM control switches control the switching states of IDPWM switching devices. The inverting and noninverting characteristics are achieved with low voltage stresses and hence low dv/dt across the high and low frequency-controlled switches. This reduces their voltage rating and losses. The high voltage overshoot problem in frequency step-up operation is also analyzed. The sliding mode (SM) controller is employed to solve this problem. Pulse selective approach determines the power quality of load voltage. The validity of the mathematically computed values is carrie...
Applied Sciences
Single-phase direct frequency converters are gaining attraction at the research and academic leve... more Single-phase direct frequency converters are gaining attraction at the research and academic level as they are rapidly getting space over conventional multistage converters. The converters developed with a rectification and inversion process using a DC-link level are examples of multistage converters with some serious concerns such as an increase in the overall weight, losses, and cost. They also suffer from the low-reliability issue due to the issues involved with DC-link capacitors and problems linked with electromagnetic interference (EMI) caused by high-frequency pulse width modulation (PWM) switching. These problems are addressed with line frequency switching cycloconverters. In these converters, the power quality of the output voltage is improved by governing the amplitude of some selected output pulses or half-cycles. For this purpose, a low-frequency multiple tapping transformer may be used to obtain various voltage levels. However, its use is the main source of increased ov...
Pakistan Journal Of Neurological Surgery, 2020
Background & Objectives: Severe traumatic brain injury is one of the leading causes of mortality ... more Background & Objectives: Severe traumatic brain injury is one of the leading causes of mortality and morbidity.Efficient management of severe traumatic brain injury demands a specialty driven focused intensive care. We developed our model of closed ICU driven by Neurosurgical Neurointensivist and the corollary to thiscommitment is a TBI patient centered Neurocritical care with the capacity and capability to deal with most of the neurological illnesses.Materials & Methods: A prospective study was conducted to find out the impact of the establishment of closed system of neurocritical care on 5 year mortality of severe TBI. Total 1288 patients met the inclusion criteria, which were enrolled. Tabulation was done for gender, age range, Glasgow outcome scale and mortality.Results: It was observed that mortality reduced from 47% to 35% over a span of five years. The most common age range was 30-40 years, which is the most productive group of any population. Bed sore incidence is always on ...
Energies, 2022
Variable voltage and frequency are required to govern the torque-speed characteristics of many in... more Variable voltage and frequency are required to govern the torque-speed characteristics of many industrial drive systems. Traditionally, this is achieved with a power converting system implemented with multistage converters. This technology is based on rectifying AC power into DC and then DC into AC with an inverter circuit. The power quality concerns of both conversion stages are tackled by selecting high switching frequency PWM control and harmonics mitigation filters. Also, using a bulky DC-link capacitor is one of the big sources of low system reliability, so this approach increases the conversion losses, circuit, and control complications. The frequency step-down conversion is very attractive with direct AC-AC converters as it has a simple control and circuit structure, but these converters face poor power quality challenges once the output frequency is decreased with respect to an input. In these converters, the total harmonic distortion (THD) of the output voltage becomes very...
Surgical Neurology International, 2021
Background: Pediatric anemia has a high prevalence in developing countries such as Pakistan. It i... more Background: Pediatric anemia has a high prevalence in developing countries such as Pakistan. It is common knowledge among hospital specialties but little is done to manage this condition by hospitalists. The issue is compounded with a poor primary care infrastructure nationally. The aim of this study is to bring to light the high prevalence of anemic children in neurosurgery and to describe the difficulties in managing their anemia in a tertiary hospital setting. A literature review is presented highlighting the socioeconomic difficulties that contribute to this widespread comorbidity and the difficulty in managing it from a hospital specialty point of view. Methods: A prospective descriptive case series was carried out between March 2020 and September 2020. All patients under the age of 13 who presented to our department for traumatic brain injury (TBI) meeting our inclusion and exclusion criteria were enrolled and assessed for the presence and severity of anemia. Demographic data ...
Background: Backache is second most common problem presenting to the primary healthcare providers... more Background: Backache is second most common problem presenting to the primary healthcare providers. Lumbar discectomy has been revolutionized from open conventional discectomy to endoscopic removal. Endoscopic procedures are proving their superiority regarding good outcome, less wound site pain and shorter hospital stay, in Neurosurgery as well. Micro discectomy and Endoscopic discectomy is used only in few centres in Pakistan. This study aimed to share our experience of early surgical outcome endoscopic lumbar discectomy in terms postoperative pain improvement and duration of hospital stay Methods: This prospective study was carried out at Neurosurgery Department, Jinnah Hospital, Lahore from Jan 2014 to Jan 2016. During this period, 35 patients of both sexes, aging between 20 and 60 years, with symptoms and signs of lumbago with sciatica were enrolled. Data was collected on a questionnaire after informed verbal and written consent. Results: A total of 35 patients were operated incl...
Applied Sciences, 2021
Single-phase and three-phase AC-AC converters are employed in variable speed drive, induction hea... more Single-phase and three-phase AC-AC converters are employed in variable speed drive, induction heating systems, and grid voltage compensation. They are direct frequency and voltage controllers having no intermediate power conversion stage. The frequency controllers govern the output frequency (low or high) in discrete steps as per the requirements. The voltage controllers only regulate the RMS value of the output voltage. The output voltage regulation is achieved on the basis of the various voltage control techniques such as phase-angle, on-off cycle, and pulse-width modulation (PWM) control. The power quality of the output voltage is directly linked with its control techniques. Voltage controllers implemented with a simple control technique have large harmonics in their output voltage. Different control techniques have various harmonics profiles in the spectrum of the output voltage. Traditionally, the evaluation of power quality concerns is based on the simulation platform. The val...
Applied Sciences, 2021
The attractive features of the direct AC-AC converters increase their use in many applications su... more The attractive features of the direct AC-AC converters increase their use in many applications such as voltage control for a heavy-duty load that has a high time constant, AC machine drives, and heating systems based on the induction process. These converters process power in single-stage having simple circuit topologies with reduced switching devices and circuit components. These characteristics lead to the efficient power conversion process. The use of a low-frequency input transformer with multiple output tapping for the regulation of output voltage and frequency is one of the major sources of cost, size, and conversion losses. The complication in the switching algorithms is also the main concern in these converters. The preceding deficiencies lower their potency to be used in daily life. The costly controllers or processors are to be employed to realize the complex control techniques or algorithms. That increases the overall cost and circuit complication. This paper introduces t...
Journal of the Pakistan Medical Association, 2020
Objective: To identify the deficiencies in patient note record-taking with the aim of improving t... more Objective: To identify the deficiencies in patient note record-taking with the aim of improving the quality to meet international standards. Methods: The prospective clinical quality improvement audit study was conducted at the department of Neurosurgery, Allama Iqbal Medical College, Jinnah Hospital Lahore from January 219 to February 2020. The first audit cycle was carried out in July 2019, after data anonymisation, the notes from 1st January to 31st June were analysed in the first audit cycle against a hybrid proforma containing entries deemed essential in operative notes according to the guidelines of the Royal College of Surgeons of England. The guidelines were subsequently disseminated among postgraduate trainees using various methods. Post-intervention, randomly selected patient-notes from 1st August to 31st December 2019 were analysed in the second audit which was done in February 2020. The result of the two audits were compared to assess significance of association between ...
Surgical Neurology International, 2020
Background: Intraoperative imaging addresses the limitations of frameless neuronavigation systems... more Background: Intraoperative imaging addresses the limitations of frameless neuronavigation systems by providing real-time image updates. With the advent of new multidetector intraoperative computed tomography (CT), soft tissue can be visualized far better than before. We report the early departmental experience of our intraoperative CT scanner’s use in a wide range of technically challenging neurosurgical cases. Methods: We retrospectively analyzed the data of all patients in whom intraoperative CT scanner was utilized. Out of 31 patients, 24 (77.4%) were cranial and 8 (22.6%) spinal cases. There were 13 male (41.9%) and 18 (58.1%) female patients, age ranged from 1 to 83 years with a mean age of 34.29 years ±17.54 years. Seven patients underwent spinal surgery, 2 cases were of orbital tumors, and 16 intra-axial brain tumors, including 5 low- grade gliomas, 10 high-grade gliomas, and 1 colloid cyst. There were four sellar lesions and two multiloculated hydrocephalus. Results: The int...
Pakistan Journal Of Neurological Surgery, 2019
Objectives: To highlight the role of public sector hospitals in sharing the major burden of sever... more Objectives: To highlight the role of public sector hospitals in sharing the major burden of severely head injured patients in a resource constrained economically striving countryMaterials and Methods: The study was conducted in the Neurosurgery department of Jinnah Hospital, Lahore, Pakistan. 70 patients with moderate to severe TBI cases above one year of age were included. The data was analyzed for the cost estimation for the period of six months, for the following heads: 1) hospital cost per day, 2) ICU setup cost per day, and 3) salaries of hospital staff per day.Results: There were 53 cases of moderate injury and 17 cases of severe injury. Mean hospital stay was 14 days, minimum number of stay was 2 days and the maximum number of stay was 124 days in six months. Overall, in six months, per day cost of hospital bills head was Rs. 42,333/$ 263/€ 238. For the ICU setup head, the total cost was Rs. 17,9923/$1130/€ 1016 per day. The salary head’s total cost was Rs. 2573/$16.06/€ 14.4...
Pakistan Journal Of Neurological Surgery, 2019
Objective: We evaluated the frequency of post traumatic amnesia (PTA) in close mild traumatic bra... more Objective: We evaluated the frequency of post traumatic amnesia (PTA) in close mild traumatic brain injury (TBI) via. Galveston Orientation and Amnesia Test (GOAT).Materials & Methods: A total of 115 patients with mild TBI, both male and female, aged between 14 to 60 years and presenting within the first 6 hours were included. Assessment with the GOAT was performed within 6 hours of admission. Post traumatic amnesia was recorded.Results: Patients’ mean age was 39.21 years. Majority of the patients (64.34%) were between 36- 60 years of age. Prevalence of post traumatic amnesia (PTA) in closed mild TBI was found in 27.83% patients, whereas, there was no post traumatic amnesia in 72.17% patients. Mean admission GCS was 14.54 and the mean GOAT score was 83.89 in all patients GCS 14/15. There was more prevalence of PTA in age 36-60 years, in male patients and “time since injury” in >3 hours. Mean GOAT was 68.3 in patients (30.19%) with PTA with GCS 14, whereas, mean GOAT was 74.8 in p...
Energies, 2019
In this research, a new single-phase direct AC-to-AC converter, operating in buck and boost mode,... more In this research, a new single-phase direct AC-to-AC converter, operating in buck and boost mode, with a bipolar voltage gain, is proposed. The operation is accomplished through high frequency direct and indirect PWM control of a single switch with low voltage stresses. This reduces, not only the control effort, but also the switching losses. The low voltage stresses across the high frequency switches, reduce the dv/dt problem significantly without any loss and bulky voltage snubber arrangement. The operation, in its all-operating modes, has a low inductor ripple current and switching current. The proposed converter may be employed as an AC voltage restorer in a power distribution system to cope with the voltage sag and swell issues. The detailed analysis of the proposed converter is carried out in order to compare its performance with the existing converters. The simulation results obtained using the MATLAB/Simulink environment are verified through experimental results.
Journal of neurological surgery. Part A, Central European neurosurgery, Jan 18, 2018
The use of single/dual external ventricular drains (EVD) for reducing intraventricular hemorrhag... more The use of single/dual external ventricular drains (EVD) for reducing intraventricular hemorrhage (IVH) is under investigation. A randomized controlled trial was conducted to compare postoperative reduction of IVH volume using single- and dual-catheter drainage in spontaneous IVH patients. We investigated factors that may influence an effective hematoma volume reduction by EVDs. The average cerebrospinal fluid (CSF) drainage volumes were analyzed. Computed tomography (CT) scans were performed on admission, 24 hours and 48 hours after EVD placement, and then on days 5 and 8. Patient group 1 was treated with a single EVD; patient group 2 was treated with bilateral EVDs. The IVH volume was calculated in all ventricles. A multivariate analysis was conducted to investigate variables that can influence the extent of hematoma volume reduction with a bilateral EVD. Regression followed by a Pearson correlation was performed to observe the strength of association of cofounders with the IVH ...
2017 International Conference on Electrical Engineering (ICEE), 2017
The controlled ac-to-dc converters are used to control the output dc voltage. A six pulses contro... more The controlled ac-to-dc converters are used to control the output dc voltage. A six pulses controlled ac-to-dc converter is one of the efficient converters that is widely used in many industrial applications. The main advantage of any higher pulse converter in ac-to-dc conversion is low ripple factor but on the other hand, it highly distorts the input supplied currents. This distortion degrades the power factor, and increases the stresses across the protective devices and measuring units in the power system, hence exhibits poor power quality. It becomes important to analyze the power quality in ac-to-dc power conversion. A new approach called pulse selective method is introduced to analytically calculate the harmonics in a three phase rectifier circuit both for input and output. Then power quality performance parameters are analyzed on the basis of computed harmonics. Simulation modeling is used to verify the proposed method.