Design of a Solar Tracking System Using the Brightest Region in the Sky Image Sensor.

Solar energy is certainly an energy source worth exploring and utilizing because of the environmental protection it offers. However, the conversion efficiency of solar energy is still low. If the photovoltaic panel perpendicularly tracks the sun, the solar energy conversion efficiency will be improved. In this article, we propose an innovative method to track the sun using an image sensor. In our method, it is logical to assume the points of the brightest region in the sky image representing the location of the sun. Then, the center of the brightest region is assumed to be the solar-center, and is mathematically calculated using an embedded processor (Raspberry Pi). Finally, the location information on the sun center is sent to the embedded processor to control two servo motors that are capable of moving both horizontally and vertically to track the sun. In comparison with the existing sun tracking methods using image sensors, such as the Hough transform method, our method based on the brightest region in the sky image remains accurate under conditions such as a sunny day and building shelter. The practical sun tracking system using our method was implemented and tested. The results reveal that the system successfully captured the real sun center in most weather conditions, and the servo motor system was able to direct the photovoltaic panel perpendicularly to the sun center. In addition, our system can be easily and practically integrated, and can operate in real-time.

Developing an effective arterial stiffness monitoring system using the spring constant method and photoplethysmography.

This study aimed to develop a fast and effective arterial stiffness monitoring system for diabetic patients using the spring constant method and photoplethysmography (PPG). The experimental group comprised 70 patients (4 type 1 diabetes mellitus patients and 66 type 2 diabetes mellitus patients); 23 participants suffered from atherosclerosis. All were subjected to the measurements of both the carotid-femoral pulse wave velocity (cfPWV) and the spring constants evaluated using the PPG pulse as well as the radial pulse. The control group comprised 70 normal participants (39 men and 31 women) who did not have diabetes mellitus, with an age range of 40-84 years. All control group members were only subjected to the measurement by the spring constant method. For the experimental group, statistical analysis indicated a significantly high correlation between the spring constants computed using PPG and the radial pulse (p < 0.001, correlation coefficient =0.89). The result also showed a significant negative correlation between the cfPWV and the spring constant of PPG (p < 0.001, correlation coefficient = - 0.72); multivariate analysis similarly indicated a close relationship. In addition, we used Student's t test to examine the difference between the experimental and control groups for the spring constant of PPG. A P value less than 0.05 confirmed that the difference between the two groups was statistically significant. In the receiver operating characteristic curve, area under curve (=0.82) indicates a good discrimination, and a spring constant of PPG below 516 (g/s (2)) may imply a risk of arterial stiffness for diabetic patients. These findings imply that the spring constant of PPG could effectively identify normal versus abnormal characteristics of elasticity in normal and diabetic participants. As a result of some excellent characteristics in clinical monitoring, the spring constant computed using PPG shows the effectiveness and feasibility in the monitoring system of arterial stiffness.

Analysis of using the tongue deviation angle as a warning sign of a stroke.

BACKGROUND: The symptom of tongue deviation is observed in a stroke or transient ischemic attack. Nevertheless, there is much room for the interpretation of the tongue deviation test. The crucial factor is the lack of an effective quantification method of tongue deviation. If we can quantify the features of the tongue deviation and scientifically verify the relationship between the deviation angle and a stroke, the information provided by the tongue will be helpful in recognizing a warning of a stroke. METHODS: In this study, a quantification method of the tongue deviation angle was proposed for the first time to characterize stroke patients. We captured the tongue images of stroke patients (15 males and 10 females, ranging between 55 and 82 years of age); transient ischemic attack (TIA) patients (16 males and 9 females, ranging between 53 and 79 years of age); and normal subjects (14 males and 11 females, ranging between 52 and 80 years of age) to analyze whether the method is effective. In addition, we used the receiver operating characteristic curve (ROC) for the sensitivity analysis, and determined the threshold value of the tongue deviation angle for the warning sign of a stroke. RESULTS: The means and standard deviations of the tongue deviation angles of the stroke, TIA, and normal groups were: 6.9 ± 3.1, 4.9 ± 2.1 and 1.4 ± 0.8 degrees, respectively. Analyzed by the unpaired Student's t-test, the p-value between the stroke group and the TIA group was 0.015 (>0.01), indicating no significant difference in the tongue deviation angle. The p-values between the stroke group and the normal group, as well as between the TIA group and the normal group were both less than 0.01. These results show the significant differences in the tongue deviation angle between the patient groups (stroke and TIA patients) and the normal group. These results also imply that the tongue deviation angle can effectively identify the patient group (stroke and TIA patients) and the normal group. With respect to the visual examination, 40% and 32% of stroke patients, 24% and 16% of TIA patients, and 4% and 0% of normal subjects were found to have tongue deviations when physicians "A" and "B" examined them. The variation showed the essentiality of the quantification method in a clinical setting. In the receiver operating characteristic curve (ROC), the Area Under Curve (AUC, = 0.96) indicates good discrimination. The tongue deviation angle more than the optimum threshold value (= 3.2°) predicts a risk of stroke. CONCLUSIONS: In summary, we developed an effective quantification method to characterize the tongue deviation angle, and we confirmed the feasibility of recognizing the tongue deviation angle as an early warning sign of an impending stroke.

Using the spring constant method to analyze arterial elasticity in type 2 diabetic patients.

BACKGROUND: This study tests the validity of a newly-proposed spring constant method to analyze arterial elasticity in type 2 diabetic patients. METHODS: The experimental group comprised 66 participants (36 men and 30 women) ranging between 46 and 86 years of age, all with diabetes mellitus. In the experimental group, 21 participants suffered from atherosclerosis. All were subjected to the measurements of both the carotid-femoral pulse wave velocity (cfPWV) and the spring constant method. The comparison (control) group comprised 66 normal participants (37 men and 29 women) with an age range of 40 to 80 years who did not have diabetes mellitus. All control group members were subjected to measurement by the spring constant method. RESULTS: Statistical analysis of the experimental and control groups indicated a significant negative correlation between the spring constant and the cfPWV (P < .001; r = - 0.824 and - 0.71). Multivariate analysis similarly indicated a close relationship. The Student's t test was used to examine the difference in the spring constant parameter between the experimental and control groups. A P-value less than .05 confirmed that the difference between the 2 groups was statistically significant. In receiver operating characteristic curve (ROC), the Area Under Curve (AUC, = 0.85) indicates good discrimination. These findings imply that the spring constant method can effectively identify normal versus abnormal characteristics of elasticity in normal and diabetic participants. CONCLUSIONS: This study verifies the use of the spring constant method to assess arterial elasticity, and found it to be efficient and simple to use. The spring constant method should prove useful not only for improving clinical diagnoses, but also for screening diabetic patients who display early evidence of vascular disease.

Radial pressure pulse and heart rate variability in normotensive and hypertensive subjects.

OBJECTIVES: The characteristics of the right/left radial pressure pulse (RPP) at the six diagnosis positions in Chinese medicine are not well documented. The purpose of this study is to investigate the spectral energy and augmentation index (AI) of bilateral RPP at the six diagnosis positions and heart rate variability (HRV) in the normotensives, hypertensives without heart dysfunction (HTN-N), and hypertensives with mild diastolic dysfunction (HTN-A). DESIGN: One hundred and thirty-eight (138) subjects were enrolled in this study. All subjects underwent measurements of brachial arterial blood pressure and RPP of both wrists while seated, and the supine measurement of HRV. AI and spectral energy of RPP as well as HRV were analyzed. RESULTS: The low-frequency component, the spectral HRV parameter, was significantly reduced in HTN-A compared with that in the normotensive group. Radial AI of the six diagnosis positions in HTN-N was significantly higher compared with that in the normotensive group or HTN-A. At the six diagnosis positions, the spectral energy of 0-10 Hz (SE(0-10 Hz)) in both hypertensive groups and 10-50 Hz (SE(10-50 Hz)) in the HTN-A group were significantly higher compared with those in the normotensive group. SE(10-50 Hz) at right Chy, left Chun, and left Guan in the HTN-N group were higher than those in the normotensive group. Within each group, there was a significant difference in the energy proportion, 10-50 Hz% (EP(10-50 Hz%)), between the six positions and a significant reduction only at the left Chun position in both hypertensive groups compared to that in the normotensive group. CONCLUSIONS: It is concluded that the EP(10-50 Hz%) revealed the specific characteristics of RPP and significantly varied at the six positions, and the left Chun position, the position to detect the heart diseases in Chinese medicine, is qualified to discriminate the differences between the normotensive and hypertensive patients.

An innovative method to measure the peripheral arterial elasticity: spring constant modeling based on the arterial pressure wave with radial vibration.

In this study, we propose an innovative method for the direct measurement of the peripheral artery elasticity using a spring constant model, based on the arterial pressure wave equation, vibrating in a radial direction. By means of the boundary condition of the pressure wave equation at the maximum peak, we can derive the spring constant used for evaluating peripheral arterial elasticity. The calculated spring constants of six typical subjects show a coincidence with their proper arterial elasticities. Furthermore, the comparison between the spring constant method and pulse wave velocity (PWV) was investigated in 70 subjects (21-64 years, 47 normotensives and 23 hypertensives). The results reveal a significant negative correlation for the spring constant vs. PWV (correlation coefficient = -0.663, p < 0.001). Multivariate analysis also indicates the same close relationship. Furthermore, within-operator and between-operator analyses show significantly high reproducibility. Therefore, the use of the spring constant method to assess the arterial elasticity is carefully verified, and it is shown to be effective as well as fast. This method should be useful for healthcare, not only in improving clinical diagnosis of arterial stiffness but also in screening subjects for early evidence of cardio-vascular diseases and in monitoring responses to therapy in the future.

Developing the effective method of spectral harmonic energy ratio to analyze the arterial pulse spectrum.

In this article, we analyze the arterial pulse in the spectral domain. A parameter, the spectral harmonic energy ratio (SHER), is developed to assess the features of the overly decreased spectral energy in the fourth to sixth harmonic for palpitation patients. Compared with normal subjects, the statistical results reveal that the mean value of SHER in the patient group (57.7 ± 27.9) is significantly higher than that of the normal group (39.7 ± 20.9) (P-value = .0066 < .01). This means that the total energy in the fourth to sixth harmonic of palpitation patients is significantly less than it is in normal subjects. In other words, the spectral distribution of the arterial pulse gradually decreases for normal subjects while it decreases abruptly in higher-order harmonics (the fourth, fifth and sixth harmonics) for palpitation patients. Hence, SHER is an effective method to distinguish the two groups in the spectral domain. Also, we can thus know that a "gradual decrease" might mean a "balanced" state, whereas an "abrupt decrease" might mean an "unbalanced" state in blood circulation and pulse diagnosis. By SHER, we can determine the ratio of energy distribution in different harmonic bands, and this method gives us a novel viewpoint from which to comprehend and quantify the spectral harmonic distribution of circulation information conveyed by the arterial pulse. These concepts can be further applied to improve the clinical diagnosis not only in Western medicine but also in traditional Chinese medicine (TCM).

Application of sphygmography to detection of dyspepsia and the rhinitis.

Diagnosis by radial arterial pulse is very important in Traditional Chinese Medicine (TCM). The objective of this study is to evaluate the effects of detection time and position on the parameters of time- and frequency-domain of radial pulse wave and to differentiate between Dyspepsia and Rhinitis by the statistical analysis of two signal types. A sphygmograph was developed to record radial pressure pulse for spectral analysis. The measurements were expressed as the pressure wave and its frequency. In this study, 135 subjects including the controls, Dyspepsias and Rhinitis were enrolled in this study. The signals were taken from three diagnosis positions of both wrists. Seven parameters of pressure wave and two parameters of spectrum analysis were evaluated by ANOVA test and Tukey's test. The results showed that the effects of detection time and position on the parameters taken from pulse wave were inconsistent. No regular rules or relationship could be established. The power spectra of 10-50 Hz and 13-50 Hz from sphygmography revealed a significant effect of health status, position and their interaction. There was a significant difference in the power spectra of 13-50 Hz between the control and Rhinitis, as well as between the control and Dyspepsia at right Guan position. The results of this study strongly suggest that the spectrum of sphygmogram might be more helpful than the pressure wave signals for detection of Dyspepsia and Rhinitis.

Radial pressure pulse and heart rate variability in heat- and cold-stressed humans.

This study aims to explore the effects of heat and cold stress on the radial pressure pulse (RPP) and heart rate variability (HRV). The subjects immersed their left hand into 45°C and 7°C water for 2 minutes. Sixty healthy subjects (age 25 ± 4 yr; 29 men and 31 women) were enrolled in this study. All subjects underwent the supine temperature measurements of the bilateral forearms, brachial arterial blood pressure, HRV and RPP with a pulse analyzer in normothermic conditions, and thermal stresses. The power spectral low-frequency (LF) and high-frequency (HF) components of HRV decreased in the heat test and increased in the cold test. The heat stress significantly reduced radial augmentation index (AIr) (P < .05), but the cold stress significantly increased AIr (P < .01). The spectral energy of RPP did not show any statistical difference in 0 ~ 10 Hz region under both conditions, but in the region of 10 ~ 50 Hz, there was a significant increase (P < .01) in the heat test and a significant decrease in the cold test (P < .01). The changes in AIr induced by heat and cold stress were significantly negatively correlated with the spectral energy in the region of 10 ~ 50 Hz (SE(10-50 Hz)) but not in the region of 0 ~ 10 Hz (SE(0-10 Hz)). The results demonstrated that the SE(10-50 Hz), which only possessed a small percentage in total pulse energy, presented more physiological characteristics than the SE(0-10 Hz) under the thermal stresses.

Influence of menstrual cycle on pulse pressure waveforms measured from the radial artery in biphasic healthy women.

OBJECTIVES: The aim of this study was to investigate the effects of the menstrual cycle on the pulse pressure waveforms in women with regular biphasic cycles. METHODS: We recruited 36 biphasic healthy eumenorrheic volunteers. Pulse pressure waveforms from the radial artery were recorded by sphygmography in both hands, each with three measurement positions and three different preload pressures, in a total of 18 measured points. The experimental design was single blinded and the technician who measured the waveforms did not know the menstrual time point of the subjects. The parameters included the pulse rate (PR), the height of the main wave (h(1)), the height of the dicrotic wave (h(3)), the rapid ejection time, the single systolic area (sSA), and the 1-minute systolic area (tSA). RESULTS: Our results showed that PR was significantly greater during the luteal phase (81.5 +/- 1.5/minutes versus 78.3 +/- 1.5/minutes, p < 0.05) with an accompanying greater h(1), h(3), sSA, and tSA (p < 0.05). We also demonstrated that h(1), h(3), sSA, and tSA increased with preload pressures and decreased when the detector was moved proximally, possibly a resultant of differences in the diameter and depth of radial artery. Furthermore, we found that h(3) taken from the right hand was larger than that taken from the left hand and may reflect a shorter and simpler route of the right radial artery. CONCLUSIONS: We conclude that pulse waveforms taken from the radial artery may assist in the identification of greater plasma volume, ventricular ejection volume, and vasodilatation increase in the luteal compared to the follicular phase.

The exponential decay characteristic of the spectral distribution of blood pressure wave in radial artery.

This study analyzed the exponential decay characteristic of the harmonic peaks in the spectrum of blood pressure wave (BPW) from radial artery at wrist. Low-order harmonic deviation (LHD), high-order harmonic deviation (HHD), total harmonic deviation (THD) and exponent (alpha) were developed to assess the exponential decay feature of normal subjects (N group) and the patients with palpitation (P group). The statistical results indicate that only the HHD (p value=0.01<0.05) of N group is significantly less than that of P group while LHD (p value=0.08>0.05), THD (p value=0.22>0.05) and alpha (p value=0.23>0.05) make no significant differences. The results imply that the spectral harmonic peaks for patient subjects exhibit more severe deviations in high-order harmonics along the exponential decay curve than those for normal subjects. In conclusion, this paper proposes a novel viewpoint to observe how the heart distributes blood into arterial system under normal and abnormal situations in spectral domain.

Variation Analysis of Sphygmogram to Assess Cardiovascular System under Meditation.

In this article, we studied how meditation affects the characteristics of the cardiovascular system, mainly based on blood pressure waveforms (BPW). Four parameters derived from BPW include the rising slope (h(1)/t(1)), normalized height of T wave (h(3)/h(1)), normalized height of V(3) valley (h(4)/h(1)) and normalized height of D wave (h(5)/h(1)), where t(1) and h(i), i = 1, ... ,5 are quantitative features of the BPW waveform pattern. A larger value of h(1)/t(1) reflects better heart ejection ability and aorta compliance. A larger value of h(3)/h(1) may infer an arterial system with good elasticity. The decrease (increase) of h(4)/h(1) parameter indicates the decrease (increase) of peripheral resistance of vessels. A larger value of h(5)/h(1) indicates better artery elasticity and aortic valve function. In comparison with the control group, Zen-meditation practitioners have more after-meditation h(1)/t(1), h(3)/h(1) and h(5)/h(1) increase, with more h(4)/h(1) decrease, with statistical significance (P < 0.05). The observation allows us to infer that Zen meditation may effectively improve relevant characteristics of the cardiovascular system.