Recursive all-lag reference-code correlators

An all-lag reference-code correlator generates an all-lag even-or odd-correlation vector at a rate equal to the rate of incoming data samples. Direct implementation of an all-lag reference-code correlator requires N parallel correlators, and the resultant degree of complexity is of the order N2, where N is the length of the reference code. This paper derives two recursive forms for all-lag reference-code correlators. One generates all-lag even correlation and the other one generates all-lag odd correlation. It is shown that the proposed recursive all-lag reference-code correlator can be implemented with a complexity approximately equal to that of a single parallel correlator. That is, the degree of complexity of the proposed recursive all-lag reference-code correlator is of the order N. Thus, substantial reduction in the implementation complexity is achieved.published_or_final_versio

An all-lag rotating-reference correlator and its efficient implementation

This paper proposes an all-lag correlator that employs a rotating reference code sequence. The proposed correlator has an advantage over the previously proposed all-lag correlator, which employs a fixed reference code, in that correlation peaks remain at the same output positions regardless of update from newly arrived data samples. Therefore, the correlation information can be more conveniently manipulated in certain applications, and the posterior signal processing requirement can be reduced. Low-complexity implementation of the correlator using a recursive form is also presented. The degree of implementation complexity is of the order N, the reference-code length.published_or_final_versio

A recursive all-lag reference-code correlator for generating odd correlations

An all-lag reference-code correlator generates an all-lag even- or odd-correlation vector at a rate equal to the rate of incoming data samples. Direct implementation of an all-lag reference-code correlator requires N parallel correlators, and the resultant degree of complexity is of the order N 2, where N is the length of the reference code. In a previous paper, a recursive form for generating all-lag even correlations was derived. In this paper, we derive the recursive form for generating all-lag odd correlations. It is shown that the corresponding correlator can be implemented with a complexity approximately equal to that of a single parallel correlator. That is, the degree of complexity of the proposed recursive all-lag reference-code correlator is of the order N. Thus, substantial reduction in the implementation complexity is achieved.published_or_final_versio

The state of quality management implementation : a cross-sectional study of quality-oriented companies in Hong Kong

Author name used in this publication: Kee-hung LaiAuthor name used in this publication: T. C. E. Cheng2001-2002 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Recursive all-lag reference-code correlator and its efficient implementation

An all-lag reference-code correlator generates an all-lag correlation vector at a rate equal to the rate of incoming data samples. Direct implementation of an all-lag reference-code correlator requires N parallel correlators, and the resultant degree of complexity is of the order N2, where N is the length of the reference code. This paper derives a recursive form for the all-lag reference-code correlator. It is shown that the proposed recursive all-lag reference-code correlator can be implemented with a complexity approximately equal to that of a single parallel correlator. That is, the degree of complexity of the proposed recursive all-lag reference-code correlator is of the order N. Thus, substantial reduction in the implementation complexity is achieved.published_or_final_versio

Cerebrospinal fluid to serum glucose ratio in non-hypoglycorrhachic neurological conditions

Objective. To explore the relevance of cerebrospinal fluid to serum glucose ratio in non-hypoglycorrhachic conditions. Design. Retrospective observational study. Setting. Neurology ward, university teaching hospital, Hong Kong. Patients. Adult patients with conditions unrelated to hypoglycorrhachia who underwent lumbar puncture. Main outcome measures. Cerebrospinal fluid and simultaneous serum glucose concentrations, and their ratio to each other. Results. Between September 1998 and August 2003, 170 cerebrospinal fluid and serum glucose samples were collected from 138 patients. Mean cerebrospinal fluid to serum glucose ratio was 0.61 (standard deviation, 0.142; range, 0.21-1.00). With the exception of cerebrospinal fluid protein level, laboratory parameters were similar among different diseases. The glucose ratio was lower than 0.6 in 43% and lower than 0.5 in 19% of samples. Cases with a low glucose ratio appeared to have higher serum glucose concentrations (significant among groups with different glucose ratios, P<0.001). The mean glucose ratio (0.65) was also significantly higher in patients with serum glucose concentration of lower than 7.8 mmol/L compared with those with serum glucose concentration between 7.8 and 11.1 mmol/L (mean, 0.46), or higher than 11.1 mmol/L (mean, 0.46) [P<0.001]. There was a strong negative correlation between the glucose ratio and serum glucose concentration (r= -0.704, P<0.001). Conclusion. A lowered cerebrospinal fluid to serum glucose ratio is often seen in the absence of an appropriate disorder, especially when simultaneous serum glucose concentration is elevated. This may be explained by the saturation kinetics of glucose transportation in hyperglycaemia, and the time lag for cerebrospinal fluid and glucose to equilibrate when the blood level fluctuates.published_or_final_versio

An epidemiological study of motor neuron disease in Hong Kong

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Clinical relevance of severe initial hypertension in acute intracerebral haemorrhage

Free Paper Presentations – Session 2OBJECTIVE: To characterise severe initial hypertension (SIH) in the acute intracerebral haemorrhage (ICH) and the related clinical outcomes. METHODOLOGY: We prospectively identified patients admitted to a regional hospital with acute ICH between January 2003 and September 2003. SIH was defined by systolic BP >180 mmHg, diastolic BP >105 mmHg and/or mean BP >130 mmHg for 2 or more readings at 10 or more minutes apart. Clinical data was recorded and analyzed. The modified Rankin score was used to assess disability. RESULTS: A total of 102 patients were identified. SIH was found in 72 patients (70.6%). Comparing those with SIH and those without SIH, they differed statistically in Glasgow Coma Scale (p=0.03), National Institutes of Health Stroke Scale (p<0.001), volume of ICH (p=0.006), past history of hypertension (p=0.03) and time from onset to hospital arrival (p=0.013). Patients with SIH had a statistically significant increase in 30-day mortality (p=0.028) and 3-month mortality (p=0.016) as well as increase in 30-day disability (p=0.003) and 3-month disability (p=0.006). However, the correlation between SIH and mortality or disability was lost when controlling for the above factors. Furthermore, about half of the patients with SIH had their BP subsided within the first day, and this was associated with a significantly lower 30-day disability (p=0.033) and 3-month disability (p=0.045). CONCLUSION: SIH in acute ICH is related to a poor neurological state, an increased volume of ICH, a past history of hypertension and a shorter delay from onset. SIH is a prognostic indicator for mortality and disability but is not an independent factor. As those with early settle of BP have a lower disability, aggressive BP control in the acute phase of ICH may lessen the morbidity.published_or_final_versio

A prevalence study of epilepsy in Hong Kong

Objectives. To examine epidemiological data on epilepsy for the Hong Kong west region. Design. Descriptive study. Setting. Epilepsy clinic, university teaching hospital, Hong Kong. Patients and methods. The epilepsy clinic of Queen Mary Hospital manages the majority of adult patients (aged 15 years or older) with chronic seizure disorders resident in the Hong Kong west area with an adult population of 475 900. All patients underwent electroencephalography examination and each subject was independently assessed by two epileptologists for diagnosis and classified according to the International League Against Leaoue Epilepsy recommendations. Results. Seven hundred and thirty-six patients (female, 42.9%; male, 57.1%; mean age, 40.8 years; standard deviation, 13.6 years) with epilepsy were enrolled in the study. The prevalence rate of active epilepsy in the population 15 years or older was estimated at 1.54 per 1000 on 1 January 2002. Two hundred and eighty-five (38.7%) patients had idiopathic epilepsy syndromes, 100 (13.6%) had cryptogenic epilepsy, and 285 (38.7%) had a remote symptomatic aetiology. Seizure type was partial in 408 (55.4%) patients and generalised in 285 (38.7%). Thirty-one (4.2%) patients had a positive family history. Idiopathic generalised epilepsy syndromes described as common in the literature, such as juvenile myoclonic epilepsy and childhood absence epilepsy, were infrequently seen at 0.68% and 0.95% of cases, respectively. Conclusions. This study provides baseline data for epilepsy service development and research in Hong Kong. The prevalence rate of active epilepsy in this Chinese, adult population was low compared with that reported in other developed countries. Further population-based epidemiological research is indicated to confirm the prevalence of seizure disorders in this locality.published_or_final_versio

Predictive factors for ischemic strokes complicating tuberculous meningitis

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