Calibration of Portable Particulate Matter–Monitoring Device using Web Query and Machine Learning

BACKGROUND: Monitoring and control of PM(2.5) are being recognized as key to address health issues attributed to PM(2.5). Availability of low-cost PM(2.5) sensors made it possible to introduce a number of portable PM(2.5) monitors based on light scattering to the consumer market at an affordable price. Accuracy of light scattering–based PM(2.5) monitors significantly depends on the method of calibration. Static calibration curve is used as the most popular calibration method for low-cost PM(2.5) sensors particularly because of ease of application. Drawback in this approach is, however, the lack of accuracy.METHODS: This study discussed the calibration of a low-cost PM(2.5)-monitoring device (PMD) to improve the accuracy and reliability for practical use. The proposed method is based on construction of the PM(2.5) sensor network using Message Queuing Telemetry Transport (MQTT) protocol and web query of reference measurement data available at government-authorized PM monitoring station (GAMS) in the republic of Korea. Four machine learning (ML) algorithms such as support vector machine, k-nearest neighbors, random forest, and extreme gradient boosting were used as regression models to calibrate the PMD measurements of PM(2.5). Performance of each ML algorithm was evaluated using stratified K-fold cross-validation, and a linear regression model was used as a reference.RESULTS: Based on the performance of ML algorithms used, regression of the output of the PMD to PM(2.5) concentrations data available from the GAMS through web query was effective. The extreme gradient boosting algorithm showed the best performance with a mean coefficient of determination (R²) of 0.78 and standard error of 5.0 μg/m³, corresponding to 8% increase in R² and 12% decrease in root mean square error in comparison with the linear regression model. Minimum 100 hours of calibration period was found required to calibrate the PMD to its full capacity. Calibration method proposed poses a limitation on the location of the PMD being in the vicinity of the GAMS. As the number of the PMD participating in the sensor network increases, however, calibrated PMDs can be used as reference devices to nearby PMDs that require calibration, forming a calibration chain through MQTT protocol.CONCLUSIONS: Calibration of a low-cost PMD, which is based on construction of PM(2.5) sensor network using MQTT protocol and web query of reference measurement data available at a GAMS, significantly improves the accuracy and reliability of a PMD, thereby making practical use of the low-cost PMD possible.

Control of Industrial Safety Based on Dynamic Characteristics of a Safety Budget-Industrial Accident Rate Model in Republic of Korea

BACKGROUND: Despite the recent efforts to prevent industrial accidents in the Republic of Korea, the industrial accident rate has not improved much. Industrial safety policies and safety management are also known to be inefficient. This study focused on dynamic characteristics of industrial safety systems and their effects on safety performance in the Republic of Korea. Such dynamic characteristics are particularly important for restructuring of the industrial safety system. METHODS: The effects of damping and elastic characteristics of the industrial safety system model on safety performance were examined and feedback control performance was explained in view of cost and benefit. The implications on safety policies of restructuring the industrial safety system were also explored. RESULTS: A strong correlation between the safety budget and the industrial accident rate enabled modeling of an industrial safety system with these variables as the input and the output, respectively. A more effective and efficient industrial safety system could be realized by having weaker elastic characteristics and stronger damping characteristics in it. A substantial decrease in total social cost is expected as the industrial safety system is restructured accordingly. CONCLUSION: A simple feedback control with proportional–integral action is effective in prevention of industrial accidents. Securing a lower level of elastic industrial accident-driving energy appears to have dominant effects on the control performance compared with the damping effort to dissipate such energy. More attention needs to be directed towards physical and social feedbacks that have prolonged cumulative effects. Suggestions for further improvement of the safety system including physical and social feedbacks are also made.

Effectiveness of Direct Safety Regulations on Manufacturers and Users of Industrial Machines: Its Implications on Industrial Safety Policies in Republic of Korea

BACKGROUND: Despite considerable efforts made in recent years, the industrial accident rate and the fatality rate in the Republic of Korea are much higher than those in most developed countries in Europe and North America. Industrial safety policies and safety regulations are also known to be ineffective and inefficient in some cases. METHODS: This study focuses on the quantitative evaluation of the effectiveness of direct safety regulations such as safety certification, self-declaration of conformity, and safety inspection of industrial machines in the Republic of Korea. Implications on safety policies to restructure the industrial safety system associated with industrial machines are also explored. RESULTS: Analysis of causes in industrial accidents associated with industrial machines confirms that technical causes need to be resolved to reduce both the frequency and the severity of such industrial accidents. Statistical analysis also confirms that the indirect effects of safety device regulation on users are limited for a variety of reasons. Safety device regulation needs to be shifted to complement safety certification and self-declaration of conformity for more balanced direct regulations on manufacturers and users. An example of cost-benefit analysis on conveyor justifies such a transition. CONCLUSION: Industrial safety policies and regulations associated with industrial machines must be directed towards eliminating the sources of danger at the stage of danger creation, thereby securing the safe industrial machines. Safety inspection further secures the safety of workers at the stage of danger use. The overall balance between such safety regulations is achieved by proper distribution of industrial machines subject to such regulations and the intensity of each regulation. Rearrangement of industrial machines subject to safety certification and self-declaration of conformity to include more movable industrial machines and other industrial machines with a high level of danger is also suggested.

Practicality of thermography in evaluation of osteoarthritis of knee joint

BACKGROUND: About 80 percent of the Korean population over 55 years old show radiographic signs of osteoarthritis. Hence, osteoarthritis has become one of the most important public health problem among the old age. Despite the importance of this disease, proper methods for evaluation and diagnosis of osteoarthritis have not been developed. Authors have investigated the sensitivity and specificity of thermography in diagnosing osteoarthritis. METHODS: Twenty patients who had visited the department of family medicine, Korea University Hospital, with non-traumatic knee pain during the period from April 1 to May 30, 1999, were included in the study. Patients had gone through series of careful history taking, physical examination and laboratory evaluations for clinical evaluation of osteoarthritis of the knee joints. Furthermore, the radiographic and thermographic examination of both knee joints were assessed. RESULTS: Among the twenty patients who have been examined, 15 patients were to have shown radiographic abnormality; on the other hand, 14 patients showed thermographic abnormality. Seventeen patients showed clinical manifestations of osteoarthritis. Twelve patients, among those who had clinical osteoarthritis, were shown to have osteoarthritis in both image studies, i.e. radiographic and thermographic abnormalities. All patients who had not shown clinical osteoarthritis, were normal on both image studies. The sensitivity and specificity of thermography in diagnosing osteoarthritis were 80% and 80%, respectively (P<0.05). CONCLUSIONS: Hot spots or asymmetric distribution in the knee joint area of osteoarthritis patients were in thermographic examination. Thermography has shown efficacy in the evaluation of osteoarthritis.

Usefullness of Thermography in Migraine Diagnosis

Background : The reports from researchers present new imaging diagnosis, which makes it possible to observe the vascular change(temperature change) of face in migraine. However, we do not have enough study for thermography to find out migraine in Korea. thus, this study was performed in order to apply thermography to migraine patients. Methods : From November in 1989 to July in 1999, patients with headache who visited to Korea University Hospital Family Medicine were undertaken. Among them, 6 patients who were appropriated for the International Headache Society criteria for migraine were performed facial thermography. Results : Six patients who were appropriate for IHS criteria for migraine were undertaken in this study. When they had headache attack, we tested thermography. Asymmetry of heat loss on supraorbital and frontotemporal areas was not significantly different in three of them. The others showed the difference of heat loss more than 0.5 degrees C in supraorbital and frontotemporal areas. It was in headache side that heat loss was showed. Two of patients who showed heat loss were enable to follow up and one of them showed the disappearance of asymmetrical heat loss. Conclusions : As a result, facial thermograms demonstrated the significant differences in heat loss from the temple and orbits in migraine patients. We concluded thermography in migraine patients is suitable for clinical use

Usefulness of Thermography in Diabetic Neuropathy

Background : diabetic neuropathy is one of the serious complication of diabetes mellitus and it can cause serious foot problems. These foot problems could be preventable if early detection method of diabetic neuropathy is established. Therefore, essential diagnostic tool is needed. The changes on electrophysiologic studies(EPS) may to be necessarily correlated with clinical neuropathy. Theater has attempted to confirm the thermography as an useful tool for detecting diabetic peripheral neuropathy. Methods : Author has studied 20 patients with diabetes visiting to department of family medicine of Korea University Hospital between December 1, 1998 and June, 30, 1999. All cases were evaluated on clinical criteria. Furthermore, the EPS and thermography have been taken. The author investigated the results of thermograpy and the relation of the clinical diagnosis and EPS. Results : among 20 cases, 12(60.0%) cases have shown abnormality on EPS and 6(30.0%) cases of them was also abnormal on clinical criteria, the other 8(40.0%) cases were normal on EPS. Results of EPS were moderately related to clinical diagnosis. 10(50.0%) cases have shown abnormality on thermography and 6(30.0%) cases of them were also abnormal on clinical criteria, the other 10(50.0%) cases were normal on thermography. Results of thermography were related to clinical diagnosis. Among 12(60.0%) cases were abnormal on EPS, 9(45%) cases also have shown abnormality on thermography. Among 8(40.0%) cases were normal on EPS, 7(35.0%) cases were also normal on thermography. Results of thermography were highly related to EPS. Conclusion : Thermography is a useful diagnostic tool in diabetic peripheral neuropathy.