A Node Localization Algorithm for Wireless Sensor Networks Based on Virtual Partition and Distance Correction

The coordinates of nodes are very important in the application of wireless sensor networks (WSN). The range-free localization algorithm is the best method to obtain the coordinates of sensor nodes at present. Range-free localization algorithm can be divided into two stages: distance estimation and coordinate calculation. For reduce the error in the distance estimation stage, a node localization algorithm for WSN based on virtual partition and distance correction (VP-DC) is proposed in this paper. In the distance estimation stage, firstly, the distance of each hop on the shortest communication path between the unknown node and the beacon node is calculated with the employment of virtual partition algorithm; then, the length of the shortest communication path is obtained by summing the distance of each hop; finally, the unknown distance between nodes is obtained according to the optimal path search algorithm and the distance correction formula. This paper innovative proposes the virtual partition algorithm and the optimal path search algorithm, which effectively avoids the distance estimation error caused by hop number and hop distance, and improves the localization accuracy of unknown nodes.

Radiographic Outcomes of Proximal vs Distal Syndesmotic Low Tibial Osteotomy

Background: We aimed to determine whether the location of tibial osteotomy affects the outcome during low tibial osteotomy (LTO) with fibular osteotomy for varus ankle arthritis by comparing proximal syndesmotic (PS) and distal syndesmotic (DS) tibial osteotomy. Methods: We retrospectively reviewed the radiographic findings of 50 cases (among 47 patients) who underwent LTO with fibular osteotomy for varus ankle arthritis. The enrolled patients were divided into 2 groups according to the location of the tibial osteotomy: the PS group (25 cases, 24 patients) and the DS group (25 cases, 23 patients). Radiographic parameters were compared between the 2 groups. Results: There were no significant differences in tibial anterior and lateral surface angles, tibiomedial malleolar angle, talar center migration, and intermalleolar distance correction between the 2 groups (all P > .05). However, the decreases in talar tilt (TT) and talocrural angle (TCA) were more pronounced in the DS group than in the PS group (both P < .05). Among patients with TT ≥8 degrees, a greater decrease in TT (+1.0 degrees vs –2.8 degrees) and TCA was observed in the DS group, whereas the PS group demonstrated greater increases in TCA and intermalleolar distance (all P < .01). Conclusion: In this series, DS tibial osteotomy combined with fibular osteotomy was a more effective operative option than PS tibial osteotomy to correct both extra- and intra-articular deformity for varus ankle arthritis. Level of evidence: Level III, retrospective comparative study.

Design and Development of a Low Cost, Non-Contact Infrared Thermometer with Range Compensation

Fever is a common symptom of many infections, e.g., in the ongoing COVID-19 pandemic, keeping monitoring devices such as thermometers in constant demand. Recent technological advancements have made infrared (IR) thermometers the choice for contactless screening of multiple individuals. Yet, even so, the measurement accuracy of such thermometers is affected by many factors including the distance from the volunteers’ forehead, impurities (such as sweat), and the location measured on the volunteers’ forehead. To overcome these factors, we describe the assembly of an Arduino-based digital IR thermometer with distance correction using the MLX90614 IR thermometer and HC-SR04 ultrasonic sensors. Coupled with some analysis of these factors, we also found ways to programme compensation methods for the final assembled digital IR thermometer to provide more accurate readings and measurements.

Design and Development of a Low Cost, Non-Contact Infrared Thermometer with Range Compensation

Fever is a common symptom of many infections e.g. COVID-19 in the ongoing pandemic, keeping monitoring devices like thermometers in constant demand. Recent technological ad-vancements in thermometers have the infrared (IR) thermometers as the thermometer of choice for screening multiple individuals in a contactless manner. Yet, even so, the measurement accuracy of such thermometers is affected by many factors including the distance from the volunteer’s fore-head, impurities (such as sweat) and the location measured on the volunteer’s forehead. To overcome such factors, we describe the assembly of an Arduino-based digital IR thermometer with distance correction using the MLX90614 IR thermometer and HC-SR04 ultrasonic sensors. Coupled with some analysis of these factors, we also found ways to programme compensation methods for the final assembled digital IR thermometer to provide more accurate readings and measure-ments.

Biometry, Refractive Errors, and the Results of Cataract Surgery: A Large Sample Study

The statistical characteristics of biometry and refractive error in a large sample of cataractous Cuban patients are presented, comparing between sexes and age groups. All patients were studied at the Cuban Institute of Ophthalmology “Ramón Pando Ferrer,” La Habana. The sample consists of 28252 eyes of 25068 patients, subjected to cataract surgery during the time period between 2006 and 2019. Their biometry was obtained using IOL Master devices; also, visual acuity, refraction, and corneal power were registered. After surgery, the visual acuity and refraction were measured. The refractive prediction error was determined. For patients with both eyes registered, anisometropia was also calculated. Age and sex were used to segment the data. The preoperative biometric parameters show highly significant differences between sexes, with male eyes being longer and with a deeper anterior chamber but with a thinner lens. Also, keratometry shows highly significant differences, with female eyes being steeper than male. Before surgery, both sexes have myopic eyes as average, with males being more myopic than females ( p < 0.001). After surgery, the average spherical equivalent is −0.36 D and female eyes are more myopic than males ( p < 0.001). Visual acuity with and without distance correction has a significant increase after surgery. These results are of importance not only for Cuba but also for other countries with a large Cuban population and/or similar ethnic composition, such as the USA (particularly the south of Florida), Spain, and many countries in Latin America.

Determination of Local Magnitude for Earthquakes Recorded from the Texas Seismological Network (TexNet)

In this study, we present a local magnitude (ML) relation for the earthquakes recorded from the Texas Seismological Network (TexNet) between the dates of 1 January 2017 and 31 July 2019. Using a comprehensive seismic dataset from earthquakes in Texas, we propose a distance correction term −logA0, which is consistent with the original definition of the Richter magnitude. The proposed distance correction calculation for the TexNet events accounts for the attenuation characteristics of the direct and refracted waves over different distance ranges. Regression analysis of Wood–Anderson amplitudes results in the following trilinear function, which represents the attenuation attributes of the events under investigation: −logA0={2.07×log(Rhyp)+0.0002×(Rhyp−100)−0.72Rhyp≤16 km1.54×log(Rhyp)+0.0002×(Rhyp−100)−0.0816 km&lt;Rhyp≤105 km,0.29×log(Rhyp)+0.0002×(Rhyp−100)+2.45Rhyp&gt;105 km in which Rhyp is the hypocentral distance (km). The derived distance correction relationship results in an accurate ML relationship for Texas that is unbiased over a 200 km distance range. Compared with other ML relations, the proposed relation in this study gives lower ML values over all distances than those calculated by Richter (1958), Hutton and Boore (1987), Babaie Mahani and Kao (2019), and Quinones et al. (2019) by an average of 0.01, 0.12, 0.16, and 0.15 units, respectively; this study’s proposed relation gives higher ML values over all distances than those calculated by Scales et al. (2017), Yenier (2017), and Greig et al. (2018) by an average of 0.28, 0.01, and 0.08 units, respectively.

IMPROVED INDOOR POSITIONING USING BLE DIFFERENTIAL DISTANCE CORRECTION AND PEDESTRIAN DEAD RECKONING

Recently, indoor positioning becomes a popular issue because of its corresponding location-aware applications. Owing to the limits of the sheltered signal of satellites in indoor environments, one of the alternative scheme is Bluetooth Low Energy (BLE) technology. BLE device broadcasts Received Signal Strength Indicator (RSSI) for distance estimation and further positioning. However, in the complex indoor environment, the reflection, fading, and multipath effect of BLE make the variable RSSI and may lead to poor quality of RSSI. In this study, the concept called Differential Distance Correction (DDC) is similar to the Differential Global Navigation Satellite System (DGNSS). This method can eliminate some residuals and further improve the results with the corrected distance. On the other hand, Pedestrian Dead Reckoning (PDR) is another common indoor positioning method. PDR can propagate the next position from the current position by the implemented of inertial sensors. Despite that, the error of inertial sensors would accumulate with time and walking distance, which position update is required for restraining the drift. Accordingly, the two indoor positioning methods have their strong and weak point. BLE-based positioning is absolute positioning, while PDR is relative positioning. This study proposes a concept that combines the two methods. The pedestrian receives the RSSI and records the information from inertial sensors simultaneously. Through the complementary of two methods, the positioning results would be improved from 29% to 66% according to different travelled distance.

Calibration of Local Magnitude Scale for Colombia

ABSTRACT New calibration for local magnitude (ML) was performed for Colombia. The territory was divided into five zones using reported attenuation values for different areas of the country and correlating this information with the mapped lithologies, the absence or presence of volcanic activity, and patterns in the hypocentral locations of seismicity. Seismic data from the Colombian National Seismic Network—Colombian Geological Survey (RSNC-SGC) were used to obtain a total of 81,232 peak amplitudes from 22,816 earthquakes recorded between January 2015 and August 2017. This set of data was incorporated into a linear inversion to calculate the distance-correction functions for each zone. A new methodology is proposed for calculating the base level of the distance-correction function or parameter c, using the amplitude values for earthquakes with moment magnitudes (Mw) close to 3 measured at stations at distances close to 100 km. The distance-correction logA0 functions obtained in this study for the five zones are: Zone 1:−logA0=1.245×log(r)+0.0024×r−2.051,Zone 2:−logA0=1.056×log(r)+0.0021×r−1.76,Zone 3:−logA0=1.07×log(r)+0.0013×r−1.531,Zone 4:−logA0=1.241×log(r)+0.0015×r−2.178,Zone 5:−logA0=0.711×log(r)+0.0009×r−0.69, in which r is the hypocentral distance in kilometers. The results of this study are in use in the RSNC-SGC since September 2018. Before using the equations presented here, the values of local magnitude were previously underestimated for the entire Colombian territory. This work allows the calculation of the local magnitude using the largest attenuation changes in addition to decreasing discrepancies with other magnitude types such as Mw and those calculated by international networks.