Many organisms rely on densely packed, tilted and curved fibers of various dimensions to attach to surfaces. While the high elastic modulus of these fibers enables an extremely large number of fibers per unit area, where each fiber stands freely without sticking to its neighbors, the tilt/curvature provides them with the compliance and the directional adhesion properties to attach strongly and efficiently to a surface. Recent studies have revealed that many of such organisms also feature materials with a graded elastic modulus that is tailored towards improving the contact area without sacrificing the fiber density. In particular, for male ladybird beetles, research has shown that the adhesive setae feature a material gradient such that the elastic modulus of the material at the junction between the stalk and the divergent distal end is close to minimum. This soft material acts like a flexible joint, improving the bending compliance of the tip. Here, we mimic this feature using tilted, mushroom-like, stiff fibers comprised of a stiff stalk of elastic modulus 126 MPa, a softer tip of elastic modulus 8.89 MPa, and a joint-like element of elastic modulus 0.45 MPa (very soft), 8.89 MPa (soft), or 126 MPa (stiff) in between. The results from load–drag–pull (LDP) experiments performed along (gripping) and against (releasing) the tilt direction indicate that the soft and the very soft joint fibers performed superior to the stiff joint fibers and maintained directionally dependent performance. The soft joint fibers achieved up to 22 kPa in shear and 110 kPa in pull-off stress in the gripping direction, which are twice and ten times higher than that in the releasing direction, respectively. A model to optimize the elastic modulus of the joint-like elements to enable sliding without peeling of the tips has been proposed. Most natural organisms that rely on temporary adhesion to surfaces for survival do so using tiny, densely packed fibers –2. TheseInspired by the directional adhesion features attributed to the tilted setal arrays of the gecko, considerable attention has been paid to fabricating various tilted fiber/pillar arrays and studying their adhesive performance both theoretically and experimentally –22. MurpIn the work by Wang , a methoCoccinella septempunctata), a joint of soft material between the setal stalk and the tip of an individual fiber has been discovered 35].The results of this study show that the addition of a flexible joint, that is, a joint more flexible than the stalk of the fiber, between the tip and the stalk improves both shear and pull-off stresses. There seems to be an optimal flexibility beyond which no added benefit in shear or pull-off stress is observed. Indeed, although very soft joint fibers were able to maintain superior average shear stress at higher preload, pull-off stress was reduced compared to the soft joint fibers. We hypothesize that the improvement in performance with a flexible joint observed in this work is due to the added articulation and the resulting enhancement in the adaptability of the tip to the substrate. It is this enhancement, which reduces the tensile stress at the tip, preventing peel, and allows the tips to stay in adhesive contact during sliding. Fibers with flexible joints exhibit high pull-off stress because they maintain contact during the dragging portion of the test. One detriment of a flexible joint could be that it increases performance in both the gripping and the releasing directions, potentially diminishing the anisotropic characteristic of the adhesive. This can be remedied in the future by creating tips that are tilted. The effect of the fiber tip angle has been shown to improve anisotropy by Murphy et al.  and Parnx–y-positioning stage . Two goniometers  are located on the x–y-positioning stage, which control roll and pitch angles. Two precision linear stages  are attached to the goniometer assembly and they are configured to displace in the plane Y–Z where Z represents the perpendicular to the surface movements and Y represents the parallel to the surface movements. Two 500-gr load cells (GSO-500 Transducer Techniques) are attached to the precision stages, which allow forces in the Y and Z directions to be measured  and the whole system, including the stage controller is governed by a custom Labview software that is able to control preload, contact time, displacements, velocities in the Y–Z plane and record the data from two load cells.Both the fabrication of the bent stalk and the LDP experiments were performed using a custom setup. This setup is comprised of an inverted microscope  equipped with a manual measured . The setThe LDP experiments were performed first by attaching the load cell stem to the acrylic peg by gluing the peg to the stem when in contact with a glass slide. After the glue is allowed to cure for 30 min, the sample is lifted away from the surface. Then the fiber sample is brought in contact with the glass substrate at 10 μm/s until a set preload is reached. This step is immediately followed by the dragging stage where the sample is displaced laterally either in the direction of the tilt  of size similar to the peg is placed on a glass microscope slide mounted on the microscope stage, . An acryed shape . The exaEs = 126 MPa  The bent fibers are dipped in a soft material to conform the basis for the joints. b) A second dipping with the same soft material enlarges the complaint tip, creating a flexible base for the tip. c) The tips are finally formed using a soft polyurethane material, following a standard method to make mushroom-like tips.E = 126 MPa) and mushroom-like tips out of M-3180 . The joint-like elements are made of TC-9445 for the stiff joint, M-3180 for the soft joint, and Vytaflex-30  for the very soft joints. All the materials were cured at ambient for three days before testing.As is shown in


We studied how statistical models of morphology that are built on different kinds of representational units, i.e., models emphasizing either holistic units or decomposition, perform in predicting human word recognition. More specifically, we studied the predictive power of such models at early vs. late stages of word recognition by using eye-tracking during two tasks. The tasks included a standard lexical decision task and a word recognition task that assumedly places less emphasis on postlexical reanalysis and decision processes. The lexical decision results showed good performance of Morfessor models based on the Minimum Description Length optimization principle. Models which segment words at some morpheme boundaries and keep other boundaries unsegmented performed well both at early and late stages of word recognition, supporting dual- or multiple-route cognitive models of morphological processing. Statistical models based on full forms fared better in late than early measures. The results of the second, multi-word recognition task showed that early and late stages of processing often involve accessing morphological constituents, with the exception of short complex words. Late stages of word recognition additionally involve predicting upcoming morphemes on the basis of previous ones in multimorphemic words. The statistical models based fully on whole words did not fare well in this task. Thus, we assume that the good performance of such models in global measures such as gaze durations or reaction times in lexical decision largely stems from postlexical reanalysis or decision processes. This finding highlights the importance of considering task demands in the study of morphological processing. Processing of morphologically complex words  is an active topic in visual word recognition research. Studies on morphological processing have focused on determining whether complex words are recognized by decomposing them into their morphological constituents or whether they are stored as holistic units in our mental lexicon. A variety of cognitive models have been proposed which span from full decomposition models . Then it utilizes these stored morphs in segmenting new incoming words . Morfessor searches for a segmentation that is simultaneously compact and an accurate representation of the data. As an illustration, an extremely compact lexicon would include only letters but it would not provide a good representation of the data, whereas listing all words as whole units in the lexicon would be a very accurate but not compact representation of the data. Via the cost function based on the two-part coding scheme of the Minimum Description Length (MDL) principle , whereas a large value provides a lexicon of long units. As an example of extremes, Morfessor with an alpha value of 0.01 leads to a lexicon of units which largely resemble linguistically analyzed morphs, whereas an alpha value of 10 includes a lexicon of full forms   standard visual lexical decision combined with eye-tracking, to enable direct comparisons to the previous lexical decision study by Virpioja et al., , 2018, aTaken together, by using statistical models of morphology we study what kind of information is accessed during recognition of multimorphemic words. In particular, we are interested in the nature of the optimal units of processing  at different stages of word recognition and whether readers predict morphemes on the basis of previous ones. We additionally study to what extent particular task demands affect the kind of information used during online word recognition.Twenty-four healthy volunteers  participated in the lexical decision experiment. All were native speakers of Finnish with no diagnosed language disorders or neurological illnesses, and they were remunerated for their time. The study was approved by the Aalto University Research Ethics Committee.The word stimuli were the same as those used in Virpioja et al.,  and consIn addition to the real words, 360 pseudoword items were included. They were produced with the help of a letter n-gram model, which estimates the probabilities of sequences of letters, and followed the phonotactic rules of Finnish. The length of the pseudowords was matched to the length of the real words, and they resembled the real words also in terms of their morphological structure. The lexical decision task included altogether 720 items.Participants were instructed to decide as quickly and as correctly as possible whether the letter string on the computer screen was a real word or not in Finnish and to press the corresponding button on a response pad. If a response had not been registered within 1500 ms of the presentation of the letter string, the letter string disappeared and a new fixation point would appear on the screen. Prior to the experiment, participants performed a practice block of 16 items  to familiarize themselves with the task. The eye-movements of the participants were registered using the EyeLink 1000 eye-tracking device  simultaneously to the lexical decision task. Recording of the eye-movements was performed on the right eye only and in the pupil-only mode with a sampling rate of 1000 Hz. The letter strings were presented in the middle of the screen in black Courier New font on a light gray background. The visual angle was 0.41 degrees. Prior to the task, calibration was performed using a nine-point grid that extended over the entire computer screen. Before the presentation of the letter string, a fixation cross was presented for 500 ms slightly to the left of each word. This position was chosen to better match its relative position in Experiment We investigated the performance of various statistical models of morphology in predicting eye-movement measures during recognition of a variety of morphologically simple and complex (inflected and derived) words. A summary of the included statistical models and their basic structure is provided in Table Our first aim was to study how the MDL-based optimization principle applied in Morfessor performs with the different eye-tracking measures. To address the question of optimal units of representation at different stages of word recognition, we study the basic version of Morfessor (“Morfessor Baseline”) and three of its variants that put differential emphasis on decomposition vs. full form representations via the manipulation of the hyper-parameter alpha. A model with a high alpha value segments little, whereas for a model with a small alpha value, the segmentations are closer to linguistically analyzed morphs. Similarly to Virpioja et al., , we inclOur second aim was to investigate statistical models which predict upcoming morphological information on the basis of previously observed morphs. Whereas the Morfessor Baseline method assumes the morphs to appear independently of each other, the Morfessor CatMAP is a structured model, which assumes that words consist of prefixes, stems, and suffixes and categorical dependency between the units.In addition, we studied the performance of other statistical models of morphology that also provide self-information estimates and that offer interesting comparison points. Such models include, e.g., the supervised morph n-gram models that utilize purely linguistically pre-segmented input in their estimates. They thus differ from Morfessor, which works in an unsupervised manner and builds a lexicon of statistical morphs  without this kind of given information. We included a morph unigram model and a bigram model in the analysis. Finally, we compared the models to a word unigram model based on surface frequencies, as a simple measure of whole-word processing.In cases where model parameters needed to be tuned, the optimization was done using a lexical decision task dataset . We did not include the RTs in the analyses, as the RT and GD measures were highly correlated with a correlation value of 0.990. The measures would thus behave similarly also in the linear mixed modeling analyses. Three participants exceeded the preset error rate criterion of 15% and were excluded from the data. Also two stimulus words were excluded from the results because they shared the same stem. In cases of a single fixation on the word, GmF was entered as a missing value. In Experiment p values are presented in Table The decreases in the regression model deviance and the corresponding With respect to the question of the time-course of these effects, we focused on FFD and GmF measures see Fig. , assumedThe additional analyses including word unigram in the regression model together with each language model showed that each of the language models improved the prediction of all of the dependent measures beyond the word unigram model  which decomposes words at some morpheme boundaries and leaves others unsegmented, showed very good performance, especially with global and late reading measures (GD and GmF) but also in FFDs assumedly reflecting earlier stages of processing. This was shown both in the correlations and regression analyses and is in line with the RT results of Virpioja et al., . A MorfeOverall, the early measures were best predicted by models that assume that all morphs occur independently  and that segment words into morphemes. In the late measures, however, the models that predict morphs on the basis of previous ones and those that also allow whole words to be stored performed relatively better. This suggests that morpheme-based information is recruited early in the course of word recognition, largely in line with early decomposition accounts  participated in the experiment. The inclusion criteria were the same as those in Experiment The target word materials were the same as those used in Experiment The eye-movement recordings were performed using the same device and similar settings as those of Experiment Similarly to Experiment We included a number of setup-specific control predictors in the regression model. We evaluated different ways for modeling these control predictors and used the AIC value as a measure of the goodness of fit for the resulting model. Random intercepts were added for each subject, item, and list of words presented to the subject. Presentation order and the eye-movement launch site were included in the model as global estimates. The launch site is defined as the distance between the position of the last fixation in the previous interest area (word preceding the stimulus word) and the left border of the current interest area (stimulus word). The position of the analyzed word in the shown row of words (third or fifth word) was modeled as a per-subject slope. In sum, each regression model included as predictors random effects for subject, item and list, one language model (e.g. Morfessor 0.8), and the setup-specific control predictors .Similarly to Experiment In Experiment The decreases in the regression model deviance and the corresponding p values are presented in Table In the early measure FFD, the strongly morpheme-based models morph unigram model and Morfessor Baseline 0.01 provided the best improvements to the baseline regression model, followed by Morfessor Baseline 0.8, the morph bigram model, and CatMAP. Morfessor 10 and the word unigram model did not significantly improve the baseline model. In the late measure GmF, Morfessor 0.8 provided the best improvements, followed by the morph unigram and bigram models and CatMAP. Morfessor 0.01, Morfessor 10, and the word unigram model, while providing significant improvements, were not as good predictors of GmF as the other models.The additional analyses including word unigram in the regression model together with each language model showed that almost all of the language models improved the prediction of the dependent measures beyond the word unigram model, the only exception being Morfessor 10 in the FFD measure  as well as those based on linguistic morphemes fared well. Overall, the context-based models (CatMAP and the morph bigram model) improved their ranking in the late measure in comparison to the early measure FFD. These findings suggest that later stages of word recognition utilize largely morpheme-based representations but also those that the MDL principle finds optimal, i.e., sometimes keeping constituent boundaries unsegmented. In addition to morphological information, predictive information of previous morphemes is further utilized. Interestingly, the fully whole-word-based models Morfessor 10 and the word unigram model did not perform well in comparison to the other models even in the late eye-tracking measures when considering the full set of stimulus words.The lexical decision task used in Experiment The picture, however, looks somewhat different when comparing the relative performance of the models in short words vs. long words separately. For short words, full-form models predicted both early and late measures, even in this task. A word that can be seen in one fixation can be recognized via a full form if such a representation exists for it. In longer words, early processing seems to be governed by linguistically defined morphemes, and also at later stages there is more emphasis on models based on morphemes or an optimized combination of morphemes and full-forms. These results are consistent with findings of Bertram and Hyönä  who usedTaken together, these results suggest that under somewhat more naturalistic word recognition conditions, morpheme-based information is accessed early in the processing, whereas at later stages, the processing system takes into account different kinds of information: It utilizes predictions made on the basis of previous morphemes as well as information that is coded in the MDL principle of Morfessor 0.8, combining decomposed representations with some unsegmented morpheme combinations. This is the case at least in longer words. For short words, full-form processing seems to dominate.We studied how statistical models of morphology that are built on different kinds of representational units perform in predicting human word recognition. By using eye-tracking, we aimed to shed light on the kinds of processing units accessed at early vs. late stages of recognition of morphologically complex words. In combination with the eye-movement registrations, we used two tasks, a standard visual lexical decision task (Experiment As expected based on Virpioja et al., , the lexMorfessor models are based on the MDL principle and work to optimize the costs related to storage and computation of complex words, and different model variants differentially emphasize these constraints. Virpioja et al.,  analyzedEye-tracking allowed us to look more closely into the temporal stages of word recognition that the good performance of the models in each task stems from. Early stages of word recognition were well predicted by models based on linguistically defined morphemes as well as Morfessor Baseline 0.8 which includes a combination of segmented and non-segmented morpheme boundaries. This observation was made both in the lexical decision task of Experiment The later stages of word recognition can be assumed to incorporate several processes: semantic and syntactic access and integration of morphological constituents to a unified whole. A lexical decision task additionally incorporates licensing (see Schreuder & Baayen, Virpioja et al.,  showed tThe present results further indicate that readers predict upcoming morphs on the basis of the already seen ones. Prediction in recognition of morphologically complex words has been previously studied using the surprisal measure in phoneme prediction in the context of auditory words (Ettinger et al., We utilized statistical models of morphology based on optimization to study the recognition of morphologically complex words. By utilizing eye-tracking, we looked into temporal characteristics of multimorphemic word processing, and by manipulating the task, we gained information about the task-specificity of particular effects. In sum, the MDL-based optimization principle which segments words at some morpheme boundaries while keeping others unsegmented was found to perform well in both tasks and both at early and later stages of word recognition, supporting dual-route cognitive models of morphological processing. However, morphological decomposition appears to dominate at early stages of word recognition. At later stages, the system utilizes information of morphological constituents and, additionally, predictive information of previous morphemes. This was, however, not the case for short words in which full-form processing may take place throughout the processing chain. At least in longer words, the performance of whole-word-based models seems to primarily stem from reanalysis, licensing, and decision-related processes that are emphasized in the standard lexical decision task. In more naturalistic conditions, these models’ prediction ability decreased. The results thus highlight the importance of considering task demands when studying morphological processing. They also demonstrate that the relative weight of the full-form and decomposition routes is strongly guided by word length.


Watermarking is currently investigated as an efficient and safe method of embedding additional patient or environment-related data into the electrocardiogram. This paper presents experimental work on the assessment of the loss of ECG  diagnostic quality from the industrial standard EN60601-2-25:2015 point of view. We implemented an original time-frequency watermarking technique with an adaptive beat-to-beat lead-independent data container design. We tested six wavelets, six coding bit depth values (including the automatic noise-dependent one) and two types of watermark content to find the conditions that are necessary for watermarked ECG to maintain the compliance with International Electrotechnical Commission (IEC) requirements for interpretation performance. Unlike other authors, we did not assess the differences of signal values, but errors in ECG wave delineation results. The results of a total of 7300 original and watermarked 10 s ECGs were statistically processed to reveal possible interpretation quality degradation due to watermarking. Finally we found (1) the Symlet of 11-th order as the best of the wavelets that were tested; (2) the important role of ECG wave delineation and noise tracking procedures; (3) the high influence of the watermark-to-noise similarity of amplitude and values distribution and (4) the stability of the watermarking capacity for different heart rates in atrial rhythms.  Digital watermarking is a data processing method that is aimed at hiding auxiliary information in a data carrier according to steganography rules . The watOne of such a particular host type is the electrocardiogram signal (ECG). In its digital form, it is a discrete-time sequence of quantized values that are collected at a sampling frequency of double the highest component that is present in the signal  to satisfy sampling theorem without aliasing. However, the sequential occurrence of various bandlimited components of the ECG is more or less foreseeable thanks to physiological limitations , which aDigital watermarking is usually referred to in the context of data security ,7 as it The contribution of this paper is threefold: (1) it presents a watermarking technique based on the local variability of the ECG bandwidth; (2) it provides a systematic review of the performance of time-frequency ECG watermarking with different wavelets with the use of industrial quality reference; and (3) it proposes a simple yet effective method of adaptation of encoding bit depth to local variation of noise level. The remaining part of this paper is organized as follows: Chapter 2 provides a survey of the most important related works, Chapter 3 gives an outlook of the irreversible watermarking process, Chapter 4 presents the industrial standard for ECG measurement performance, Chapter 5 describes the experiment setup and results and Chapter 6 contains a discussion.A generalized review of watermarking techniques that had been applied to various biosignals was provided by N. Dey et al. , and theEngin et al.  proposedIn the proposal by Kaur et al. , the watIbaida et al. proposed an efficient method of low complexity to increase the integrity of the ECG and patient meta-data. In the conference paper , they prIntegrating the electrocardiogram watermarking and compression in a single time-frequency process was proposed by Tseng et al. . Unlike Recently, Jero and Ramu studied the watermarking of arrhythmic ECG signal  and propWang et al.  improvedFinally, Kavya PremChandran et al.  and Lijithe ECG is usually a multichannel signal (3–12 leads) with wave borders that are common to all leads,the ECG is considered quasi-periodic, however in practice, particularly in the presence of arrhythmia, each heartbeat has to be considered individually.The watermarking process starts with a limited ECG analysis process that is performed in time domain, and aims at the detection of heart beats and segmentation of P, QRS and T waves in each cycle. At this stage, it is important to notice that: ® by Aspel S.A., Poland). According to manufacturer-independent test results, the software meets the international industry standard for ECG measurement performance (see Chapter 4). For each heartbeat, the following meta-parameters were used in the watermarking process: P-onset, P-end, QRS-onset, R-peak, QRS-end and T-end.For the detection and wave segmentation task we used procedures from certified diagnostic software  and chopped accordingly to the length of the destination data container. The remaining part of the watermark is queued for encoding in the next available container. The watermark samples directly replace time-scale values in the container area. When watermark samples are too few to entirely fill the available container space, the length of the container is updated.The watermark data stream is then transformed to The container description is encoded in the second scale of time-scale ECG representation with 1-bit representation  in a fiThe essential part of the watermarking process is then made in the time-scale representation of the signal and is thus embraced by two complementary steps of forward and inverse wavelet transform of the same type and order. Its time-scale part consists of three principal stages :AnalysisThe extraction of watermark also includes preliminary analysis of the ECG, however this time a R-peak detection procedure is sufficient to provide synchronization to the container description structure. The watermarked carrier preserves all diagnostic features of the ECG and, therefore, is not modified by the decoding scheme. Only the forward wavelet transform is necessary, however it has to use the same wavelet (type and order) as the watermarking scheme. Watermark embedment and extraction schemes are presented in The data description structure begins at a fixed distance to the detected R-peak. It provides all necessary container description . This allows for unambiguous extraction of the watermark samples, followed by concatenation of data and transcoding to the original bit representation. The extracted watermark is always bit accurate to the original, however once the ECG is watermarked, it contains the watermark permanently (irreversible watermarking) unless purposely erased . Noise is omnipresent in any real-life measurement. In electrocardiography, the term of noise refers to any component of the record that is not related to cardiac activity. The principle of irreversible watermarking is that the secret was undetectable by statistical methods. The watermark should thus mimic the noise as good as possible in terms of amplitude and distribution of values. Since the intrinsic ECG noise varies from one heartbeat to another, best results are expected with the use of a noise tracking procedure that controls the adaptation of bit representation value in individual data containers. vp-p. This determines the coding bit depth n  that is used for watermark data storage in the container as equal to ⎡log2 (vp-p)⎤. Consequently, the value of n regulates the data capacity of each individual container. In practice, the length of the S-P section varies from beat to beat and the noise level also varies from channel to channel.For this purpose, at the first stage of the watermarking process, we apply a procedure that scans the container area  and measures the noise level –original records ‘MO’ lasting for 10 s with natural slight beat-to-beat differences, where the most representative beat is distinguished as a reference and is accompanied with measurement results, –artificial records ‘MA’ built of the repetitions of the original reference beat as many times as necessary for a 10 s section, thus having all heartbeats identical. An international multicenter project entitled ‘Common standards for quantitative electrocardiography’ (CSE) aimed at quantitative standardization of ECG measurement procedures and ended in 1989  with estTesting the wave delineation accuracy is not possible with MO files, since the results vary for individual heartbeats. The concept of reproducing the reference beat in MA files makes all beats identical and the wave delineation results independent on beat selection. Despite their misleading name, the MA files are live-recorded and are not mathematically synthesized sections of ECG. The results of each point type are sorted in time-ascending order, allowing for individual calculations of the average and standard deviation values, however not for ranking the participating programs. Testing a new software against the CSE Database consists of comparing each calculated wave border position to the 20 corresponding reference results in 125 MA files . This alIn order to establish a worldwide quality standards for automated interpretation of electrocardiographic records, the International Electrical Committee published a normative document IEC 60601-2-51  . Additionally, the normative document requires the amplitude measurement deviations to fall below ±25 µV (or 5% for amplitudes exceeding 500 µV). In the watermarking process, the amplitude accuracy can easily be controlled by adjusting the number of bits per watermark sample, which sets a compromise between amplitude accuracy and capacity of data containers. This issue was tested in one of our previous works  in a thrSince the irreversible steganography alters the content of the ECG signal, most authors make evaluation of their methods based on the Percent-Residual-Difference (PRD), which is loosely related to the possible deterioration of diagnostic value. Otherwise, using an IEC-certified interpretive software for evaluation and comparing respective results of clean and watermarked carriers, we can easily assess whether the watermarking process is suspected to cause confusion about medical findings. In the experimental part of the research that is presented beneath, we consider the medical content as fully preserved if all interval results from both clean and watermarked ECGs fall within the IEC-specified accuracy margin. To the best of our knowledge, no other research on ECG steganography used the industrial CSE/IEC-based standard as an evaluation tool. watermarking was performed with all 100 IEC/CSE test files ,each clean or watermarked ECG signal was fed into the interpretive software ,results of wave border detection were processed and checked for compliance with IEC accuracy requirements.The proposed watermarking technique (see Chapter 3) has been implemented in Matlab  and has been run in a series of experiments. For each set of watermarking parameters, three steps were performed: We also implemented the watermark extraction procedure to check the accuracy of the recovered watermark, however in all cases, we got identical data streams as expected since its bit accuracy is guaranteed by the method. wavelet type and order,coding bit depth (number of bits per watermark sample in time-frequency representation),watermark content ,host ECG content.We used the following watermarking parameters  to iterate through:We used three mother wavelets that were commonly applied for ECG compression due to their similarity to the QRS complex ,35: Daubn-bit samples that replace intrinsic noise in the data container area in the time-frequency ECG representation. The form of watermark message is expected to mimic the noise as closely as possible, making the watermark undetectable and preserving the original medical content of the host ECG. Since the original CSE records are sampled at 500 Hz with an amplitude resolution of 0.25 µV per LSB, we tested the watermarking process with n ∈ {1…5} bits per sample, corresponding to noise peak-to-peak amplitude of 0.25–8 µV. In addition to a fixed n value, being conscious of noise level variability, we implemented the automatic detection procedure (see Chapter 3.2) and tested the watermarking with a beat-to-beat adaptation of watermark coding bit depth.In the watermarking process, the secret message is first tailored into To make the watermarking undetectable, the watermark message should mimic the noise not only by the amplitude, however also by the distribution of sample values. We assumed the noise shows Gaussian distribution, which is not the case of ASCII text codes nor of numerical values. Therefore, it was worth testing whether the content of watermark influences the performance of the method. Two separate strings of equal length codes were used in the experiment as test watermarks: one composed of text message and the other being a sequence of digits. Finally, the electrocardiogram being itself a carrier of diagnostic message, offered various conditions for watermark embedment. Low heart rates enabled us to build long data containers with longer intervals between them, while high heart rates allowed for more frequent but shorter containers. Various arrhythmia types showed a difference of P-onset to QRS-end interval contribution, and in ventricular beats, the P wave was absent. For this reason, we also found it reasonable to test the dependence of the watermarking performance on the heart rate, however we left the extra-atrial beats , which was also not included in the IEC-recommended subset of CSE files and was beyond the scope of our research. dwtmode parameter to periodization in order to make time-scale representation size independent on wavelet filter length. An example case of difference between decompositions with db5 and db10 wavelets is presented in By applying different wavelets, we obtained different time-frequency decomposition results. Their pairwise comparison was made separately for each CSE file (the cycle length differed between files) and required setting the the wavelet used has an impact on the decomposition content andthe wavelet used for watermark embedment and for extraction must be the same.Obtained results show that: The wavelet type-oriented analysis of t-test. In all 60 cases, we got the value of 0, meaning that no statistically significant difference exists between the error sets. An example histogram of QRS length error distribution for 1 bit depth watermark coding with different wavelets is presented in In order to reveal possible wavelet-related differences between the interval measurement errors, for each of four interval types , we did 15 pairwise comparisons of 100-elements error sets between any two tested wavelet types using a As With automatic adjustment of coding bit depth, the watermarking performed slightly worse than with the fixed value of 4, however the difference was hardly noticeable. The efficiency of the adjustment process requires test ECGs with controlled noise level and, thus, was not tested in our experiment because of the use of CSE MA files with all identical heartbeats.n-bit resolution samples which replace the noise values in the data container part of original time-scale ECG representation. Therefore, statistical distribution of the watermark values influences the transparency of the watermarking process. This is visible in t-test. 144 such comparisons were done iterating through four interval types, six wavelet types and six values of coding bit depth (including the automatic one). The example result for QRS complex length is presented in The values of the watermark are first chopped into given t values). Short wavelets: db5, sym6 and bior2.4 seem to be more tolerant to the changes of watermark values distribution than longer wavelets.Apart from 4-bit coding producing error-free stegano ECG for all tested wavelets, improper setting of coding bit depth results in differences between textual and numerical watermarks in most cases  of different heart rates. The heart rate, however, does not proportionally shorten or lengthen individual sections of the heartbeat. Therefore, it is worth analyzing the influence of the heart rate to the watermark capacity and the average ECG distortion expressed accordingly to IEC as interval measurement error. The result of such analysis is presented in Apart from the heart rate dependence, several files in the testing set were systematically found as the source of errors. Six such files with their brief characteristics are described in The paper presents an original concept of wavelet-based irreversible watermarking of ECG based on expected variations of local bandwidth related to P, QRS and T wave positions. The novelty of our method also included continuous noise measurement and adaptation of the coding bit depth in order to best imitate the intrinsic ECG noise. The watermarking technique was implemented and was then thoroughly tested according to industrial standards of performance that are required for automated interpretive software. Consequently, the safe use area was determined where the watermarking does not change the medical content of the host ECG. We proved that the selection of the wavelet and the adjustment of the coding bit depth both play important roles in the preservation of watermarking transparency. Moreover, we found that the distribution of watermark values influences the possible error rate and that some ECG files are less suitable for hosting a watermark due to their content.For the evaluation of the watermarking, we consequently desisted from using the PRD and other purely statistical signal metrics, as loosely related to the medical content of ECG. Average distortion level that is measured by additional error of interval length measurement  is accepAlthough the PRD is commonly questioned as a comparative ECG metrics due to disregarding the distribution of medical content, we calculated its value for a single reason of juxtaposition of the watermarking transparency with other known methods . In thisThe use of a specific interpretive software in the assessment of the proposed watermarking method is probably the most controversial issue of this paper. We assume that for each wave border point, the position measurement error consists of two independent values: one is caused by the interpreting software, while the other is due to the watermarking process. The CSE database provides measurement results from real software packages and experts with an assumption that their mean value is closer to the truth (which remains unknown) than any single result. Thanks to decades of engineering effort, some recent packages shows the measurement precision below 1 ms in manufacturer-independent tests. Unfortunately, even the best (and most expensive) software is not a reference of absolute accuracy. Moreover, ECG recorders in which it would be built-in, rarely accept external records in well documented SCP-ECG format for interpretation. For this reason, we have taken IEC certified package from Ascard 6, available to us courtesy of Aspel S.A., and considered results that were obtained for watermark-free records  as the reference, not regarding how far they are from the CSE mean values. Consequently, all measurement errors we report in this paper are differences between results from watermarked records and from non-watermarked files that were returned by the same interpretive procedures. Despite our best care of repeatability of research, we are conscious that using other interpretive software may yield slightly different results.further research will show another wavelet performing even better,specific ECG content  or different ECG sampling rate will need other wavelet for optimal representation.The Symlet of 11-th order (sym11) seems to be the most adequate for watermarking of all the wavelet types we tested. The reason for this is its similarity to the ECG component  and good separation of energy between scales . Thanks to the similarity of the temporal waveform, the ECG is well represented in few neighboring time-frequency coefficients without too much of energy spread in time, which also yields low interference from the watermark to the high frequency components of P and QRS waves. At the same time, the sym11, being a relatively long filter, has steeper frequency slopes and separates the low frequency content of T wave  from the influence of the watermark container  and its description . The sym11 complies with IEC accuracy requirement in a wide range of coding bit depth and watermark and host ECG content. However, it cannot be excluded that:Preparing of watermark content plays a crucial role in maintaining the transparency of the process. Coding the watermark with inappropriate bit depth results in serious deterioration of the ECG content. For this purpose, we used a simple noise level tracking procedure, which seems to be sufficient in stable noise conditions. In the future, we aim to improve the noise analytics and implement a dynamic regularization procedure to make the watermark content even more like the intrinsic noise.Most of the literature reports suggest using the watermark for integration and storage of patient demographic or medication data. Following this hint, we tested our original method with textual and numerical data strings. Nevertheless, watermarks can also be created of data of various types, therefore, including binary data of any specific distribution is planned in future tests. Furthermore, a watermark regularization procedure is expected to alleviate the problem of watermark value distribution. bit-accurate (lossless) compression preserves the watermark, however it may be less effective,lossy compression methods destroy the watermark, unless purposely designed,further watermarking destroys the existing watermark (watermarking with meaningless data may be used to safely remove the existing watermark),inter channel dependencies  are lost.The tested irreversible watermarking method proved to provide a stable watermark capacity of ca. 140 samples per second . AssuminIt is noteworthy that watermark containers are independent data structures, however they may be linked to increase the capacity. Data within each container or linked containers have to be uniform. Otherwise, different data structures may carry various data types and, with appropriate cryptographic techniques, may require a reader-specific authorization.Making tests with the IEC-recommended subset of CSE files, we prove compliance of the watermarking process to the industrial performance standard. In fact, the IEC 60601-2-51 document requires testing wave delimitation accuracy only with atrial rhythms, where all P, QRS and T waves are present. Besides the normal ECG, the testing set includes both Bundle Branch Blocks, Hypertrophy, Wolf-Parkinson-White Syndrome and many others  and, in the presence of T-wave alternans, watermarks may interfere the T-wave contents, making identification of alternans patterns less reliable. These two cases, however, need further studying. Future variants of ECG analysis preceding the actual watermarking needs to be extended towards automatic detection and exclusion of ECG patterns where the watermark embedment is not advisable.


Health care and public health professionals rely on accurate, real-time monitoring of infectious diseases for outbreak preparedness and response. Early detection of outbreaks is improved by systems that are comprehensive and specific with respect to the pathogen but are rapid in reporting the data. It has proven difficult to implement these requirements on a large scale while maintaining patient privacy.The aim of this study was to demonstrate the automated export, aggregation, and analysis of infectious disease diagnostic test results from clinical laboratories across the United States in a manner that protects patient confidentiality. We hypothesized that such a system could aid in monitoring the seasonal occurrence of respiratory pathogens and may have advantages with regard to scope and ease of reporting compared with existing surveillance systems.We describe a system, BioFire Syndromic Trends, for rapid disease reporting that is syndrome-based but pathogen-specific. Deidentified patient test results from the BioFire FilmArray multiplex molecular diagnostic system are sent directly to a cloud database. Summaries of these data are displayed in near real time on the Syndromic Trends public website. We studied this dataset for the prevalence, seasonality, and coinfections of the 20 respiratory pathogens detected in over 362,000 patient samples acquired as a standard-of-care testing over the last 4 years from 20 clinical laboratories in the United States.The majority of pathogens show influenza-like seasonality, rhinovirus has fall and spring peaks, and adenovirus and the bacterial pathogens show constant detection over the year. The dataset can also be considered in an ecological framework; the viruses and bacteria detected by this test are parasites of a host (the human patient). Interestingly, the rate of pathogen codetections, on average 7.94% , matches predictions based on the relative abundance of organisms present.Syndromic Trends preserves patient privacy by removing or obfuscating patient identifiers while still collecting much useful information about the bacterial and viral pathogens that they harbor. Test results are uploaded to the database within a few hours of completion compared with delays of up to 10 days for other diagnostic-based reporting systems. This work shows that the barriers to establishing epidemiology systems are no longer scientific and technical but rather administrative, involving questions of patient privacy and data ownership. We have demonstrated here that these barriers can be overcome. This first look at the resulting data stream suggests that Syndromic Trends will be able to provide high-resolution analysis of circulating respiratory pathogens and may aid in the detection of new outbreaks. The availability of real-time surveillance data that can monitor the spread of infectious diseases benefits public health -3. At prSyndrome-based surveillance systems -10 incluComprehensive and uniform diagnostic test data will aid in the identification of potential outbreaks. A combination of broad respiratory pathogen testing and an internal electronic surveillance system enabled the rapid dissemination of data across the largest health care system in New York, the North Shore-LIJ Health System , during the influenza A H1N1-2009 pandemic in the New York City area. Pathogen-specific molecular testing permitted rapid (1) notification to state epidemiologists, (2) tracking of the virus so that health care resources could be managed effectively, and (3) evaluation of influenza diagnostics ,24. TodaIt is not always possible to accurately diagnose the causative agents of most infectious diseases from symptoms alone because of overlapping clinical presentation. Thus, to achieve maximal utility, infectious disease surveillance systems should move beyond syndrome-based reporting and be pathogen-specific and comprehensive, reporting on as many of the common pathogens for a particular syndrome as possible. Sensitive and specific automated molecular diagnostic systems that detect up to 4 different pathogens in a single sample have been available from in vitro diagnostic (IVD) manufacturers for some time ,28. HoweMultianalyte diagnostic tests provide the raw data needed for real-time pathogen-specific syndromic surveillance, but there remain a number of obstacles to sharing these results (reviewed in ). The obBordetella pertussis, Chlamydia pneumoniae, and Mycoplasma pneumoniae) pathogens [We describe here the implementation of a real-time pathogen-specific surveillance system that overcomes the PHI concerns noted above. BioFire Syndromic Trends deidentifies, aggregates, and exports test results from FilmArray Instruments in use in US clinical laboratories . Althougathogens ,46,47.With more than 362,000 patient results for the FilmArray RP test alone, the Trend database has many of the properties associated with big data as it applies to infectious disease . After dFilmArray Trend was originally implemented to provide BioFire customers with an up-to-date view of the respiratory and GI pathogens circulating at their institution. From the perspective of an IVD manufacturer, the most uniform and thus the simplest method of accomplishing this is to follow a bottom-out approach to data export in which the FilmArray sends data to a cloud database managed by the manufacturer, and Web views of these data are available by clinicians at the hospital that generated the data  metric is defined as the non-normalized number of RP patient test results generated each week across the Trend sites (computed as a centered 3-week moving average). To calculate the pathogen detection rate , are taken from the CDC website . Only thPathogen codetections are defined as FilmArray tests in which two or three organisms are detected. We also calculated two other measures that relate to codetections: the circulating pathogen number and the measure of interspecific encounter (MIE). Both of these time series measures are calculated for each site and week, a centered 5-week moving average is computed, and then an unweighted average of all sites is used to create a national aggregate. The 5-week moving average is used to reduce noise because of small numbers of samples within a week at some sites.1...PN are the percentage detection of the N different organisms circulating at a single site over a single week, then MIE is defined as shown in equation 1:More specifically, the circulating pathogen number is simply the count of the unique organisms detected at a site during a 1-week period. MIE is calculated from the frequencies of each organism at a site (number of positive test results for an organism divided by the number of FilmArray tests performed at that site). To reduce noise, we only include site data if more than 10 FilmArray tests were performed in that week. If PConceptually, MIE is an attempt to estimate the likelihood that a patient infected with one organism may be infected with another unique organism circulating in the population at a given period in time, resulting in a coinfection.The most general and efficient way to aggregate test results from the FilmArray instrument in a clinical laboratory is to follow a bottom-out approach to data export . In thisInitial testing of the Trend export mechanism was performed in collaboration with the clinical laboratories of the Medical University of South Carolina. This trial allowed us to develop and test auto-export functions and deidentification protocols for the Trend software. The deidentification requirement of the Health Insurance Portability and Accountability Act (HIPAA) of 1996, specifically the Safe Harbor provision, requires the removal of 18 enumerated variables that could directly or indirectly identify an individual . In accoAll sites  submitteFollowing the protocol established by Expert Determination review, the Trend software delays the export of results until the number of tests queued for export exceeds a minimum threshold for each type of FilmArray panel. In practice, this results in an average time to export of less than 2 hours from each site that has multiple instruments. A total of 99.11%  of the test results exported automatically occurred within 24 hours of test completion.The 20 sites contributing to the Trend pilot project  have theThe algorithm used to diagnose the cause of respiratory disease varies by site. More than half of the Trend sites do not enforce an institutional respiratory testing protocol and, even within sites that have a required protocol, some discretionary use of FilmArray RP is allowed. Without detailed records from each institution’s HIS, it is not possible to determine whether the FilmArray RP was used as a front line test or as a reflex test .To determine the prevalence of respiratory pathogens, we needed to expunge the Trend database of test results that are not derived from clinical patient samples. Nonpatient results come from a variety of sources including verification testing, routine quality control (QC), and proficiency testing PT; . DespiteM pneumoniae, C pneumonia, and B pertussis are detected in a small percentage (one-fiftieth) of all samples. The average percentage of each organism is relatively constant over the 4 years of data in the Trend database  and increase by more than ten-fold above their baseline detection rate . The CDCThe CDC FluView network  gathers We found that approximately 38,000 FilmArray RP tests in the Trend dataset had two or three codetections. The most common codetections observed are those involving HRV/EV, which is the pathogen with the overall highest rate of detections .From the Trend data, an MIE can be calculated as the probability of a codetection, weighted by the prevalence of each circulating pathogen at a site. Although the value of the MIE metric is higher than the actual codetection rate, it correlates well  and has This study describes BioFire Syndromic Trends, a new system for real-time reporting of widespread pathogen-specific syndromic data. Even in its pilot phase, the Trend database already has many of the features that characterize big data . The Vs The Trend RP dataset is growing at an average rate of >400,000 pathogen test results per month . Connecting the first 20 clinical sites has provided insight into the principal concerns that will be raised by the legal, information technology, and administrative departments of the HCPs that house FilmArray instruments. It should be possible, therefore, to expand the Trend installed base by 10- to 20-fold over the next few years. Similarly, the existence of Trend should enable other IVD manufacturers to build their own Trend-like systems with greater acceptance on the part of their customers, thereby allowing a more global and comprehensive surveillance perspective.The data in The key to implementing Trend clinical sites was to demonstrate that FilmArray test results can be exported without the risk of breaching PHI confidentiality either directly or through some combination of the data that were exported. Trend successfully used the Expert Determination process as prescribed by the HIPAA guidelines see , which gThe software architecture underlying the Trend system is both simple and secure: (1) no changes to the institutional firewall or LAN are needed; (2) the Trend database cannot reach back and query the FilmArray computer because of the institutional firewall, which is set to outbound data only; and (3) Trend software can only submit data to the cloud database and cannot query the database . Yet, deThe goal of an epidemiological surveillance network is to infer which infectious diseases are circulating in the general population based on testing a sample of patients . DiffereAlthough the removal of all PHI has great benefits in terms of implementation, it also has several shortcomings that complicate interpretation of the data. First, Trend cannot account for the variability in the diagnostic testing algorithms applied to the selection of samples to be tested by the FilmArray instruments. During the respiratory season, HCPs may prescreen patients with other diagnostic tests including rapid antigen or molecular assays for influenza and RSV or commercial and laboratory-developed molecular tests for a mix of other respiratory pathogens. Depending upon the sensitivity of these upstream tests, more than half of influenza and RSV for the subset of the patients screened would be excluded from the Trend dataset if the front line test is positive. This testing protocol may skew the actual prevalence of not only influenza and RSV but all other individual respiratory pathogens and coinfections detected by the FilmArray. In some institutions, testing is reserved for hospitalized patients and others at risk for developing complications of respiratory tract infections, including the very young, very old, and immunocompromised patients. So Trend data may represent a less healthy patient population and not necessarily general community prevalence. Conversely, there are sites that perform a significant number of tests for the outpatient setting. This may create variability among the clinical sites’ percent positivity and introduces a challenge to comparing pathogen intensity between sites.The uncertainties surrounding the testing algorithm and the precise patient population tested should not interfere with determining the onset, peak, and duration of the pathogen season at each institution. These limitations on the data are likely to be common among almost all current surveillance systems for similar reasons. Given these concerns, the agreement between the percent positivity of Flu A or B as determined by Trend and the percent positivity reported by CDC FluView Influenza is striking , supportThe second source of concern in the Trend dataset is a consequence of the removal of sample identification such that we cannot directly determine whether the sample was from a patient or was a nonclinical sample  and should be removed from further epidemiological analysis. We estimate that nonpatient testing makes up approximately one-fiftieth of the total FilmArray RP tests. Automated detection algorithms remove roughly one in 25 of the total RP tests, including approximately half of the nonclinical samples. With the exception of the four positive tests, the clinical samples removed by filtering should be a random sampling of all patient tests. The remaining nominal fraction of nonpatient tests has essentially no impact on the Trend evaluation of pathogen prevalence, but they do make it more difficult to perform high-resolution analysis of pathogen codetections. This is especially true for codetections of low prevalence organisms where QC positives are likely to be more common than real positives. Future updates to the FilmArray software will simplify the process by which the instrument operator can tag tests of nonpatient samples, thereby largely eliminating the need to filter such test results from the Trend database before analysis.The total positivity rate of the FilmArray RP test varies from a low of approximately one-third of tests in the summer months to a high of three-fourths of the tests in December and January. As previously observed , the virDetection of multiple respiratory viruses in the same patient has been reported before. In the Trend dataset, the rate of dual and triple codetections was approximately 7.94% 28,741/362,101), with HRV/EV as the organism most commonly observed in a codetection. Some viruses such as ADVs and the CoVs are detected in the presence of another organism approximately half of the time . In prin,101, witi) of pathogen positivity per FilmArray test and note that the sum of all pathogen frequencies can add up to more than unity because of codetections or be less than unity because of the presence of negative tests. In this regard, MIE differs from PIE because it is not a probability measure.The question of whether different respiratory pathogens interfere with, or facilitate, growth in a human host is of some interest and not well understood. With the right data, it can be studied at the population , individAs with weather forecasting, there is both a theoretical and a practical interest in predicting the next few weeks or months of the respiratory season -76. TrenThe Trend RP data show the percentage contribution of each pathogen to what is currently being detected by FilmArray RP testing . SecondPublic health agencies, which include local and state health departments and the CDC, are specifically exempt under a HIPAA provision that allows clinical laboratories to disclose PHI to the agencies for specified public health purposes . The exeGiven the movement in health care technology toward greater vertical integration of a hospital’s data, the bottom-out approach exemplified by Trend will face more competition from top-out approaches (Syndromic Trends is a novel surveillance tool for simultaneously monitoring multiple syndromic diseases that has demonstrated promise in expanding our knowledge of the epidemiology of infectious diseases. Indeed, the close correlation of seasonal respiratory viruses tracked by Trend with reported CDC ILI highlights the major contributory role of multiple respiratory pathogens beyond influenza to ILI. The national and global expansion of Trend will provide a comprehensive tool to study the impact of coinfections, understand the role of previously underappreciated pathogens, and clarify true disease epidemiology. Finally, systems such as Trend will be essential for the rapid identification of disease anomalies indicating potential emergent outbreaks, thereby providing an independent tool for public health surveillance.


With the booming development of the Internet of things (IoT) industry, the demand of positioning technology in various IoT application scenarios is also greatly increased. To meet the positioning requirements of the IoT application, we propose a distance measurement method based on phase regeneration that can provide positioning capability for IoT applications in indoor and outdoor environments. The PRG algorithm consists of two phases: coarse ranging phase and fine ranging phase. Fingerprint positioning algorithm based on Gradient Boost Decision Tree (GBDT) is used to determine coarse distance. The host machine measures the difference between the transmitted carrier phase and the received regenerative carrier phase to fix the fine distance and then the coarse distance is used to determine the carrier phase integer ambiguity. Finally, high precision ranging is realized. Simulation results show that the PRG method can achieve range finding with decimeter level precision under the 10 MHz subcarrier frequency. Positioning of node information is crucial in IoT applications. In plenty of IoT applications, the sensor node information is meaningless when the positioning is uncertain, such as wearable devices, sweeping robot et.al. Location-aware based on range finding can be widely used in IoT node ,2, compaDistance measurement is mainly divided by two methods: based on received signal strength (RSS) and time-of-flight estimation . Wang H.To address the aforementioned shortcomings, we present phase regeneration method for distance measurement, combining coarse range and fine range of ways to meet the demand of the system is simple, high precision range finding. Different positioning requirements can choose different parameters making the method is suitable for many positioning scenarios. Therefore, the range finding method based on phase regeneration has greater flexibility and scalability.The remainder of this paper is organized as follows: A detailed description of PRG method for distance measure is presented in d between the master and slave node can be expressed by:The PRG algorithm range finding model is shown in essed by:d=λ·12dϕ+The range finding signal of PRG algorithm is single-sideband modulation. The modulation block diagram is shown in The range finding signal The modulation signal can be got with frequency of The doppler shift can be ignored because the current user case of the scenario is low dynamic. Therefore, the search space of range finding signal is one dimension, the signal acquisition can be carried out by searching the frequency point of the signal.V is obtained by incoherent integration. The incoherent detection method of signal acquisition determines whether the received signal has been detected by detecting the magnitude of the incoherent integral amplitude V: if the incoherent integral amplitude V is less than the acquisition threshold value Signal acquisition is estimate the frequency of the receiving signal and then initialize the tracking loop according to these parameter to help the receiving channel to track the signal. The complex form of coherent integration is:a is the amplitude of signal, Where Without noise, the amplitude of V, so the V can be used for capture detection. From the above assumption of V have Ricean distributions in the presence signal and have Rayleigh distributions in absence of signals [We can see phase difference  signals . The RayEquation  and the Equation , and itsQ-Function. We can get the acquisition threshold can be expressed as:We can be seen from Simultaneous Equations  and 5)  5) with We assume that At 298 K ambient temperature, the power density of background thermal noise in the atmosphere is In addition, the signal-noise ratio can be denoted as:From the above derivation, we can get the conclusion that: (1) the longer coherent integration time can improve the SNR; (2) under the condition of the same false alarm rate, namely the acquisition threshold If we assume that a linear search for frequency of signal and the coherent integration time is 1 ms, the simulation result is shown in Incoherent integral amplitude in the real frequency may be less than other search cell due to noise in range finding signal , so we cannot think that signal acquisition is successful once positive test is obtained and this will also lead to a high false alarm rate. For this reason, we introduce a Tong search detector for PRG method, which is a linear search method in the form of variable search time. As illustrated in Under the condition that the false alarm rate of a single search is During the range finding signal tracking phase, first the receiver signal channel obtains the carrier frequency estimates from signal acquisition capture phase, and then fine estimates of the carrier frequency and phase is obtained by tracking loop. Finally, the replica carrier is used for phase measurement or transmission to master node.The carrier tracking discriminator defines the type of phase-locked loop and frequency-locked loop. The phase-locked loop adopts narrow noise bandwidth and can track the signal closely. The phase precision of the output carrier of phase-locked loop is most accurate, but it is more sensitive to dynamic stress than the frequency-locked loop. The frequency-locked loop adopts the wide noise bandwidth, so it has good dynamic performance and can be more robust when tracking during tolerance of high dynamic stress. However, the signal tracking is slightly less dense due to the higher of loop noise, so the precision of output carrier phase of frequency-locked loop is poor. The main factors influencing the accuracy of ranging in PRG method is carrier loop tracking accuracy to carrier phase. We adopt the phase-locked loop in the carrier tracking loop at the low dynamic scenario. A typical carrier tracking loop is shown in We can see from Two-quadrant arctangent function phase detector:Four-quadrant arctangent function phase detector:The third method uses the following:Classic Costas analog discriminator:The carrier tracking loop shown in K is loop gain and To analyze the effect of loop filter on the performance of phase-locked loop, it is necessary to start with the system function of phase-locked loop expressed as:The selection of essed by :(6)H(s)=We can be seen from Equation  that theThe selection of loop bandwidth is related to user dynamics and noise performance and the larger the loop bandwidth, the higher the tolerance of user dynamics, but the worse the noise performance. Therefore, the selection of The coherent integral gain Because there is quantization loss in the process of digital signal processing, which may bring loss to the coherence integral, the actual noise-to-noise ratio will be reduced, generally no more than 2 dB. Next we will analyze the loss of the coherent integral due to the frequency error.a is the amplitude of IF signal, The coherence integral in the Through the above analysis, we can get the need to provide better than an 1.5 m  and Wi-Fan 1.5 m . Range fThe proposed fingerprint algorithm consists of two phase: an offline phase and an online phase. During the offline phase, RSS readings and its orientation that the mobile device are facing are collected on grid of reference points(RP), and then these are stored in fingerprint database, GBDT algorithm was used to train the fingerprint database, and the relationship model between signal strength vector We assume that the signal on the branch of I and Q is subjected to non-correlated gaussian additive noise with a mean of 0 and a variance of Because PRG method adopts carrier phase to realize distance measurement, its precision is completely dependent on the tracking precision of carrier loop. The tracking accuracy of carrier loop mainly depends on thermal noise, oscillator frequency oscillation error, Allan mean square error and dynamic stress error. In this paper, the simulation experimental parameters are set follows as The mean variance of thermal noise error can be expressed as:The mean square error of Allan can be expressed as:Phase jitter caused by the mechanical vibration of user movement and the receivers of the frequency of oscillation is Then, the Under the static condition of the user, the parameter setting is the shown in In the off-line phase, the fingerprint map is constructed through signal collector, which collects RSSI of each AP through RAK476 module . The posThe cumulative distribution function(CDF) of coarse range finding error is shown in We suggest that the PRG method can achieve high precision range finding by eliminating the carrier integer ambiguity using coarse range finding method and it provides a basis for high precision positioning. Applying carrier phase measurement to study distance measurement using phase regeneration, we found that the method is both stability and accuracy, as demonstrated in the phase-locked loop results. Distance measurement accuracy was examined by comparing the PRG method and the coarse ranging finding method based on RSS. Our results in the range finding accuracy show a high precision compared to coarse range-based RSS finding method.The carrier phase measurement technology in PRG method proposed in this paper reference the GPS of measurement technology, and a general standard require the mean square error of carrier phase measurement is less than half wavelength carrier for using pseudorange to round up the carrier phase integer ambiguity algorithm , and thiThe positioning method, based on distance measurement, consists of distance measurement and geometric calculation. Distance measurement can be divided based on the time synchronization and non-synchronization measurement. It is difficult to require high precision time synchronization for positioning in some scenarios, such as IoT. The PRG method proposed in this paper is combined with RTD and carrier phase measurement, so it has the advantages of not requiring high precision time synchronization and high precision distance measurement.There are two issues that need to be studied in the future. One is the the system design and simulation verification of using Code Division Multiple Access (CDMA) signal as the range finding signal


This paper analyzes and discusses the capability of human being detection using impulse ultra-wideband (UWB) radar with an improved detection algorithm. The multiple automatic gain control (AGC) technique is employed to enhance the amplitudes of human respiratory signals. Two filters with seven values averaged are used to further improve the signal-to-noise ratio (SNR) of the human respiratory signals. The maximum slope and standard deviation are used for analyzing the characteristics of the received pulses, which can provide two distance estimates for human being detection. Most importantly, based on the two distance estimates, we can accurately judge whether there are human beings in the detection environments or not. The data size can be reduced based on the defined interested region, which can improve the operation efficiency of the radar system for human being detection. The developed algorithm provides excellent performance regarding human being detection, which is validated through comparison with several well-known algorithms. The ultra-wideband (UWB) radar has been extensively used for the remote sensing of human subjects at short distances through walls and ruins . A humanNon-invasive monitoring is more suitable for application in some situations where it is challenging to use complex wired connections, such as burn victims or electrocardiogram (ECG) monitoring for infants . UsuallyThe UWB monitoring of life signs has been widely studied in the literature ,12,13,14Based on UWB radars, life signs can be extracted accurately even in through-wall conditions, which is most important in natural disaster relief. Demodulation techniques have been used to remove random body movement in quadrature Doppler radar for life sign monitoring . A noise(1)The multiple automatic gain control (AGC) technique is employed to enhance the strength of the respiratory signals of human beings, which can better enhance human respiratory signals and reduce the noise based on the used gain values.(2)Two filters with seven values averaged are used for improving the SNR of human respiratory signals with one filter performed on the distance direction, and another filter performed on the frequency direction.(3)Two statistics, including the maximum slope and standard deviation, are used for analysing the characteristics of human respiratory signals. Based on the acquired results, the distance between the radar receiver and human beings can be calculated.(4)Based on the distance estimate, the interested region containing human respiratory signals can be determined, which can be used to improve the SNR and the accuracy of the frequency estimate of human respiratory movement.(5)The developed algorithm gives an excellent performance regarding human being detection, which is validated compared with several well-known algorithms.This paper proposes a novel algorithm for human being detection using the UWB impulse radar system. The contributions of the paper are summarized as:The four sections are discussed as follows. In Different measurements take place in the China National Fire Equipment Quality Supervision Center, and the Institute of Electronics at the Chinese Academy of Sciences. The experimental setups for human being detection are shown in To show the fundamental problem of human being detection, two male volunteers served as human beings, as shown in The first experiment was conducted as shown in As shown in As shown in As shown in This section discusses the developed algorithm for human being detection using the UWB impulse radar. The details of the developed algorithm are shown in A. The received radar data are collected in digital form, which is an M×N matrix. Several approaches have been proposed for estimating this static clutter. The exponential averaging algorithm is employed for removing the static clutter based on the time-variant weighted coefficient λ, which can be adjusted between 0 and 1. Based on the exponential averaging algorithm, we can acquire the following results , where υ corresponds to the index of the distance estimate τ1 in the distance frequency matrix. The acquired data and the signals in the interested region are shown in To estimate the frequency of human respiratory signals, the interested region containing the signals of human respiration is determined in this subsection based on the distance estimate my(n) in F, we can acquire the following results:Since the frequency of human respiratory signals is confined to a narrow frequency distance, one selected frequency window within 0.1–0.8 Hz is used for removing clutters and harmonics in very high and very low frequencies. Based on the employed frequency window, for each frequency signal To acquire the frequency of human respiratory signals, the accumulated spectrums are considered, which are given by:Usually, the maximal value in Equation (10) is defined as the frequency of human respiratory signals.This section discusses the developed algorithm for human being detection. This subsection analyzes the capability of clutters suppression based on the received data from human beings at a distance of 12 m away from the UWB impulse radar. The performances of distance estimate based on the developed algorithm are analyzed and discussed using the data acquired in different environments. Based on the radar data acquired from one human being at distances of 4 m, 7 m, 10 m, and 12 m indoors, the distance estimates are shown in In this subsection, three algorithms are employed as references, including the constant false alarm ratio (CFAR) algorithm , advanceThe performances of the frequency estimate of human respiratory signals based on the developed algorithm are analyzed and discussed using the data acquired in different environments.Based on the data acquired from the used actuator at distances of 4 m, 7 m, 10 m, and 12 m indoors, the received data and the selected signals in the interested region are shown in To validate the accuracy of the frequency estimate, the data acquired from the used actuator at different distances, including 4 m, 7 m, 10 m, and 12 m indoors, are employed as references. The frequency estimates of the used actuator at different distances based on the selected signals in the interested region are shown in This subsection validates the capability of two-target detection based on the acquired data. Further, This paper proposes a novel algorithm for human being detection using the ultra-wideband (UWB) impulse radar systems. The multiple automatic gain control (AGC) technique is employed to enhance the strength of the respiratory signals of human beings. Two filters with seven values averaged are used for improving the signal-to-noise ratio (SNR) of human respiratory signals. The maximum slope and standard deviation are used for analyzing the characteristics of human respiratory signals. Based on the acquired results, the distance between the radar receiver and human beings can be calculated. Based on the distance estimate, the interested region containing human beings can be determined, which can be used to improve the SNR and the accuracy of the frequency estimate of human respiratory movement. Our future work will mainly focus on how to extract human respiratory signals when they are in motion such as walking and running. Further, we will continue to analyze how to identify human beings from other living animals.


The functionalization of nanoparticles (NPs) with DNA has proven to be an effective strategy for self-assembly of NPs into superlattices with a broad range of lattice symmetries. By combining this strategy with the DNA origami approach, the possible lattice structures have been expanded to include the cubic diamond lattice. This symmetry is of particular interest, both due to the inherent synthesis challenges, as well as the potential valuable optical properties, including a complete band-gap. Using these lattices in functional devices requires a robust and stable lattice. Here, we use molecular simulations to investigate how NP size and DNA stiffness affect the structure, stability, and crystallite shape of NP superlattices with diamond symmetry. We use the Wulff construction method to predict the equilibrium crystallite shape of the cubic diamond lattice. We find that, due to reorientation of surface particles, it is possible to create bonds at the surface with dangling DNA links on the interior, thereby reducing surface energy. Consequently, the crystallite shape depends on the degree to which such surface reorientation is possible, which is sensitive to DNA stiffness. Further, we determine dependence of the lattice stability on NP size and DNA stiffness by evaluating relative Gibbs free energy. We find that the free energy is dominated by the entropic component. Increasing NP size or DNA stiffness increases free energy, and thus decreases the relative stability of lattices. On the other hand, increasing DNA stiffness results in a more precisely defined lattice structure. Thus, there is a trade off between structure and stability of the lattice. Our findings should assist experimental design for controlling lattice stability and crystallite shape. Nanoparticle (NP) assemblies have numerous demonstrated and predicted applications, such as optical or electronic materials, biosensing, drug delivery and others ,2,3,4. FThere have been significant advances in creating NP lattices with a broad range of lattice symmetries and lattice spacings ,15,16,24In order to better control the properties of diamond structured NP lattices, we need an improved understanding of the factors that control lattice stability and crystallite shape. NP size can potentially alter both the lattice stability as well as the optical properties of lattices, both due to changes in the NP optical properties and changes of the lattice spacing. In this work, we study the relative stability of CD superlattices as a function of NP size and DNA stiffness using molecular dynamics (MD) simulations. We evaluate the relative stability of lattices based on their free energy. We find that entropic effects dominate the changes of free energy. We break the entropic effects into the contributions from the translational and rotational degrees of freedom. We find that the translational entropy stabilizes the lattice as the NP size increases; in contrast, the rotational degrees of freedom have a destabilizing effect as the NP size increases. The contributions to the entropy from the rotational orientation outweigh those of the translational degrees of freedom. We show that we can enhance the lattice stability (lower free energy) by increasing the flexibility of the DNA strands, which in turn, increases the contribution from the rotational entropy. On the other hand, increasing the flexibility results in a less well-defined structure. Thus, from a design perspective, there is a balance between enhancing stability and optimizing the desired order. The important role played by entropy in diamond packings has been recognized previously ,36. For We also evaluate the equilibrium shape of the cubic diamond crystallites using the Wulff construction . The Wul2) ,41,42.The manuscript is ordered as follows: A four-coordinated CD lattice typically requires highly directional interactions. Experimentally, directional NP interactions were realized by placing a spherical NP in the middle of a tetrahedral cage made by DNA origami methods . These dWe first describe how we mimic the tetrahedral DNA origami “cages” that were experimentally used to create tetra-functional NP; see ollowing , the diaFor the standard FENE potential, To make the edges more rigid, next-nearest neighbor edge particles are also bonded via a FENE potential with a bond length chosen to prefer linearity among triplets. As In order to have a tetrahedral edge that mimics the rod-like nature of the tetrahedral edges in the experiment, we choose the bond length , each particle type (tetrahedron or NP) is organized in an FCC lattice.We simulate the coarse-grained model via molecular dynamics (MD) calculations, carried out using the LAMMPS simulation suite . To examb is chosen to geometrically allow for a connection between the NP and tetrahedron to form only along the nearest linking strand, preventing the formation of defects in this unit cell; this linked strand will not be stress free, but we will release this constraint later. We then perform a MD simulation of the primitive unit cell in a triclinic box with periodic boundary conditions in an NVT ensemble at temperature 0.09  and . We again use c (the unit-cell vector in the z direction) and the other 2 unit-cell vectors is a and b (unit-cell vectors) lie in the a and b are determined by the symmetry of plane. For the smallest system considered, the surface consists of 16 NPs, and the slab consists of eight layers transverse to the surface (four layers each of NP and tetrahedra). Each system consists of at least 128 NPs and tetrahedra in total. To check if our results are affected by the finite size of the slab, we performed simulations with six, eight, or ten layers of NPs for the 111 facet. The surface energy for different thicknesses was constant within the limits of uncertainty of the calculation, so we do not anticipate any finite size effects in our reported results.To find the crystallite shape of the CD lattice, we use the Wulff construction method. This method requires the values of surface energy for different crystalline plane symmetries. To evaluate the surface energy of crystal facets with different symmetries, we must create lattices that are non-periodic in the direction normal to the facet under consideration. We use the same procedure employed for the periodic lattices just described to create fully bonded lattices with an exposed face. The system consists of a slab of diamond lattice that is periodic in the plane parallel to two lattice vectors, and non-periodic normal to the free surface , (110) and (111) surfaces. Since NP only interact with their nearest neighbors (short-ranged interaction), it is expected that the lower index planes are most important . The snaAs described in the methods section, we can predict the surface energy of these interfaces from a simple “broken bond” model, assuming no distortion of the crystal structure, and compare this to a direct evaluation of surface energy from MD simulation, where interfaces may distort. In the broken bond approximation, we simply count the number of broken bonds per unit area for the chosen crystallographic plane and estimate the surface energy for each facet using the hybridization energy of DNA. This counting exercise predicts that the (111) face should have the lowest surface energy, and in this case, Wulff construction predicts the equilibrium crystallite is an octahedron, the same shape as atomic systems with diamond structure  .To test the validity of the predictions from the broken bond approximation, we evaluate the surface energy via MD simulations for slabs with facets of the same symmetries (100), (110), and (111) for NP diameter 40 and for variable values tiffness , and canThe variation in the surface energy mentally .Exploiting the possibility of surface reorientation offers a path to control the crystallite shape. One approach to affect the reorientation of particles, and consequently crystallite shape, is to change the DNA stiffness as done here. Another possible approach is to use the DNA origami method to alter the geometry of the cages, and thereby change the bonding ability of cages and NPs. The difference in the number of possible DNA linking locations between the tetrahedra (four) and NP (20), coupled with sufficient flexibility of the DNA, results in a more stable system (lower surface energy) when tetrahedral cages are on the surface than when NPs are on the surface. Such increased stability should make the crystallite more resistant to heterogeneous melting at the interface.In this work, we have not studied the effect of DNA length on the stability of the lattice. The importance of the DNA length on the stability and the quality of long-range order of the DNA-origami cages lattices has been seen experimentally . Furtherq values. For example, for stiffer DNA  ,55.n over all of unit-cells, i and j relative to the ideal separation i and two nearest neighbors j and k. The radial bond constant q, The dynamical matrix can be related to the normal mode dispersion relation by assuming a simplified harmonic model for the interactions among the lattice sites ,50. Specq for each of six branches, the number of which is determined by having two particles in each unit-cell. The symbols in We directly calculate these frequencies Equation . Since wgenerate . We focuWe now proceed to evaluate the relative thermodynamic stability as a function of particle size and DNA stiffness. To do so, we need to evaluate the change in Gibbs free energy To evaluate the lattice free energy, the Hamiltonian can be written in terms of the normal coordinates of vibration in Fourier space,We have already numerically and analytically  evaluateOur lattice free energy data  show thaFrom a design perspective, it is helpful to know how different aspects of the lattice vibrations affect the free energy. For example, how much of the stability originates from energetic versus entropic effects? The free energy is separable into energetic and entropic contributions to We wish to parse the entropy into the contributions from the rotational and vibrational degrees of freedom. In our dynamical matrix approach, the free energy (entropy) is a complicated function of s via d is the diameter of the NP or tetrahedron. Since the NP and tetrahedra are connected, the arc length s must be the same for either particle type. Thus, as NP diameter increases, The vibrational amplitudes saturate at characteristic values Based on the independent oscillator approach, the relative entropy as a function of NP size or DNA stiffness can be separated into translational and rotational degrees of freedom. In this approximation, T dependence of T dependence of The reference Equation  should adecreases with increasing NP size. increasing free energy with increasing size; we can further dissect the rotational contribution from NP and tetrahedra. For tetrahedra, Based on the values obtained for trahedra . The conThe qualitative effects of DNA stiffness  are the same for all components: increasing stiffness decreases the entropy, and thus, increases free energy. Moreover, the quantitative variation of the free energy with stiffness is simpler than is apparent in We studied the crystallite shape of the CD lattice. The specific design of the DNA-origami cage and its effect on the number of bond sites leads to a reduction in the surface energy of specific symmetries, and consequently alters the equilibrium crystallite shape. Specifically, the predicted shape of crystallite for CD lattices without surface reorientation is an octahedron, which shifts to a cube-truncated octahedron when surface reorientation is possible. We also have studied the effects of NP size and DNA stiffness on the stability of the CD lattices. We found that the increase of stiffness and NP size (in the range of this study) increase the free energy and consequently decrease the relative thermodynamic stability of these lattices. On the other hand, the increase of stiffness improves the structure of these lattices. So there is a potential trade off between having a well structured lattice or a more stable lattice. The less stiff DNA leads to a more stable system, and this effect has seen previously in the patchy particles systems . By sepa