An FPGA Acceleration and Optimization Techniques for 2D LiDAR SLAM Algorithm

An efficient hardware implementation for Simultaneous Localization and Mapping (SLAM) methods is of necessity for mobile autonomous robots with limited computational resources. In this paper, we propose a resource-efficient FPGA implementation for accelerating scan matching computations, which typically cause a major bottleneck in 2D LiDAR SLAM methods. Scan matching is a process of correcting a robot pose by aligning the latest LiDAR measurements with an occupancy grid map, which encodes the information about the surrounding environment. We exploit an inherent parallelism in the Rao-Blackwellized Particle Filter (RBPF) based algorithms to perform scan matching computations for multiple particles in parallel. In the proposed design, several techniques are employed to reduce the resource utilization and to achieve the maximum throughput. Experimental results using the benchmark datasets show that the scan matching is accelerated by 5.31-8.75x and the overall throughput is improved by 3.72-5.10x without seriously degrading the quality of the final outputs. Furthermore, our proposed IP core requires only 44% of the total resources available in the TUL Pynq-Z2 FPGA board, thus facilitating the realization of SLAM applications on indoor mobile robots

Frequency-Hopping Wave Engineering with Metasurfaces

Wave phenomena can be artificially engineered by scattering from metasurfaces, which aids in the design of radio-frequency and optical devices for wireless communication, sensing, imaging, wireless power transfer and bio/medical applications. Scattering responses vary with changing frequency; conversely, they remain unchanged at a constant frequency, which has been a long-standing limitation in the design of devices leveraging wave scattering phenomena. Here, we present metasurfaces that can scatter incident waves according to two variables - the frequency and pulse width - in multiple bands. Significantly, these scattering profiles are characterized by how the frequencies are used in different time windows due to transient circuits. In particular, with coupled transient circuits, we demonstrate variable scattering profiles in response to unique frequency sequences, which can markedly increase the available frequency channels in accordance with a factorial function. Our proposed concept, which is analogous to frequency hopping in wireless communication, advances wave engineering in electromagnetics and related fields.Comment: 62 pages, 25 figure

Sex and age-level differences of walking time in preschool children on an obstacle frame

<p>Abstract</p> <p>Background</p> <p>Stepping over an obstacle is a kind of compound movement that makes walking more difficult, especially for preschool children. This study examines sex and age-level differences in walking time in preschool children on an obstacle frame.</p> <p>Methods</p> <p>The participants included 324 healthy preschool children: four-year-old boys (51) and girls (51), five-year-old boys (50) and girls (60), and six-year-old boys (62) and girls (50). A 5 cm- or 10 cm-high obstacle (depth 11.5 cm, width 23.5 cm) was set at the halfway point of a 200 cm × 10 cm walking course.</p> <p>Results</p> <p>The participants walked to the end of the course and back as fast as possible under three conditions: no obstacle, low obstacle and high obstacle. Walking time showed age-level differences in all conditions, but there were no differences in sex. Age levels were divided into two groups, with one group within the first six months of their birthday, and the second group within the last six months of that year. Walking time for children in the first half of their fourth year was longer than that of the five- and six-year-old children. In addition, for children in the last half of their fourth year, walking time was longer than both sexes in the last half of their fifth and sixth years. The children in the latter half of their fifth year had a longer walking time in the high obstacle condition than those in the last half of their sixth year. In the four-year-old participants, walking time was shorter with no obstacles than with a high obstacle frame.</p> <p>Conclusions</p> <p>In the above data, obstacle course walking time does not show a gender difference, except that the four-year-old participants needed longer than the five- and six-year-old children. Setting the obstacle 10 cm high also produced a different walking time in the five- and six-year-old participants. The high obstacle step test (10 cm) best evaluated the dynamic balance of preschool children.</p

Sarcoidosis-associated hepatocellular carcinoma

Sarcoidosis is a systemic granulomatous inflammation of unknown etiology, and seems to involve the liver parenchyma in most cases. However, sarcoidosis-associated hepatocellular carcinoma is rare. We report here a case in which a hepatocellular carcinoma occurred within the liver, which was probably involved as a result of systemic sarcoidosis. A 57-year-old Japanese man had been followed up for 2 years because of diabetic nephropathy and sarcoidosis. On admission for pneumonia, imaging studies revealed an unexpected hepatic tumor. Histology revealed a hepatocellular carcinoma accompanied by T-lymphocytic infiltration and marked granulomatous inflammation, which was surrounding some tumor nodules. The background liver parenchyma exhibited a moderate degree of fibrosis with granulomatous inflammation. The patient had no other apparent liver disease such as viral hepatitis, steatohepatitis, or primary biliary cirrhosis. Therefore, in the present case, sarcoidosis may be considered the probable background etiology for hepatocarcinogenesis

Method for Extracting the Equivalent Admittance from Time-Varying Metasurfaces and Its Application to Self-Tuned Spatiotemporal Wave Manipulation

With their self-tuned time-varying responses, waveform-selective metasurfaces embedded with nonlinear electronics have shown fascinating applications, including distinguishing different electromagnetic waves depending on the pulse width. However, thus far they have only been realized with a spatially homogeneous scattering profile. Here, by modeling a metasurface as time-varying admittance sheets, we provide an analytical calculation method to predict the metasurface time-domain responses. This allows derivation of design specifications in the form of equivalent sheet admittance, which is useful in synthesizing a metasurface with spatiotemporal control, such as to realize a metasurface with prescribed time-dependent diffraction characteristics. As an example, based on the proposed equivalent admittance sheet modeling, we synthesize a waveform-selective Fresnel zone plate with variable focal length depending on the incoming pulse width. The proposed synthesis method of pulse-width-dependent metasurfaces may be extended to designing metasurfaces with more complex spatiotemporal wave manipulation, benefiting applications such as sensing, wireless communications and signal processing

Miniaturized Low-Pressure Ion-Exchange Module and Its Application to an Acidic Eluent Generator for Open Tubular Ion Chromatography

We describe a miniaturized eluent generator (MEG), which can be integrated into open tubular capillary column ion chromatography (OTCC-IC). The MEG consists of one central eluent channel and two feed acid chambers, with each phase isolated by a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM). Pure water flowed through the central eluent channel while acid solution (HA) was fed to both chambers. Applying the electric field to the MEG, H+ and A- simultaneously and respectively through the CEM and AEM to form HA in the central channel. The MEG successfully produced tartaric acid and 2,6-pyridinedicarboxylic acid as the eluent for cation OTCC-IC. The gradient elution improved the peak resolution and analytical window for five common cations (Na+, NH4+, K+, Ca2+, Mg2+)

Extracting and Mathematical Identifying Form of Stationary Noise in X-ray Images

Image noise may prevent proper diagnostic X-ray imaging. This study is aimed at developing new noise rejection methods using a mathematical model that describes the form of X-ray image noise. Stationary noise is one type of noise found in X-ray images. Stationary noise is nonstochastic and appears independent of the radiographic factors. In this paper, we verify methods for identifying stationary noise using a polynomial regression model, and extracting such noise from X-ray images obtained from a CR system. The results of this study demonstrate that stationary noise can be extracted with high precision using a particular low-pass filter frequency. We found that a regression model for greater than second-degree polynomials can be applied for roughly identifying stationary noise. However, the fitting accuracy of the regression curve is not significantly improved in terms of the amount of multiplication required when increasing the degree of the polynomial regression model

The mobility performance of the elderly before, during and after crossing over an obstacle

Purpose. Tripping over objects is a major cause of fall-related injuries. The elderly feature decreased locomotor velocity with aging and delays in locomotion when encountering obstacles. Numerous studies have analyzed how the mobility performance of the elderly is affected when crossing over an obstacle. However, how is mobility performance affected when performing sequences of various locomotor movements (gait, changing direction, standing up and sitting down) that make up activities of daily living? To answer this question, this study investigated the changes in locomotor velocity when encountering an obstacle during various locomotor movements in both older adults and young adults by using the TUG, a representative mobility test. Methods. Thirty older adults who were judged to be able to walk independently by the Berg Balance Scale (BSS) (age: 70.0 ± 6.94 yrs; BB S: 54.7 ± 1.78 pts) and seventeen male young adults (age: 21.7 ± 2.37 yrs) participated in the "Timed Up & Go" (TUG) test with and without an obstacle. Using the TUG score (the total time required to complete the test), a rate of the total times (with an obstacle/ without an obstacle) was calculated to create an index of the decline in mobility performance by the obstacle. Results. The decline in the mobility performance of the elderly was significantly larger than the young adults for the following measurements: in the single stance phases just before and after an obstacle, the time needed to change direction 180 degrees, and for level walking after crossing over an obstacle. Conclusions. The elderly require a longer period of time for stepping over obstacles. Gait and the ability to change direction after encountering an obstacle was found to be slower when compared to the younger male population

Neural networks for action representation: a functional magnetic-resonance imaging and dynamic causal modeling study

Automatic mimicry is based on the tight linkage between motor and perception action representations in which internal models play a key role. Based on the anatomical connection, we hypothesized that the direct effective connectivity from the posterior superior temporal sulcus (pSTS) to the ventral premotor area (PMv) formed an inverse internal model, converting visual representation into a motor plan, and that reverse connectivity formed a forward internal model, converting the motor plan into a sensory outcome of action. To test this hypothesis, we employed dynamic causal-modeling analysis with functional magnetic-resonance imaging (fMRI). Twenty-four normal participants underwent a change-detection task involving two visually-presented balls that were either manually rotated by the investigator's right hand (“Hand”) or automatically rotated. The effective connectivity from the pSTS to the PMv was enhanced by hand observation and suppressed by execution, corresponding to the inverse model. Opposite effects were observed from the PMv to the pSTS, suggesting the forward model. Additionally, both execution and hand observation commonly enhanced the effective connectivity from the pSTS to the inferior parietal lobule (IPL), the IPL to the primary sensorimotor cortex (S/M1), the PMv to the IPL, and the PMv to the S/M1. Representation of the hand action therefore was implemented in the motor system including the S/M1. During hand observation, effective connectivity toward the pSTS was suppressed whereas that toward the PMv and S/M1 was enhanced. Thus, the action-representation network acted as a dynamic feedback-control system during action observation

Examination of factors affecting gait properties in healthy older adults: Focusing on knee extension strength, visual acuity, and knee joint pain

Background and Purpose: Gait properties change with age because of a decrease in lower limb strength and visual acuity or knee joint disorders. Gait changes commonly result from these combined factors. This study aimed to examine the effects of knee extension strength, visual acuity, and knee joint pain on gait properties of for 181 healthy female older adults (age: 76.1 (5.7) years). Methods: Walking speed, cadence, stance time, swing time, double support time, step length, step width, walking angle, and toe angle were selected as gait parameters. Knee extension strength was measured by isometric dynamometry; and decreased visual acuity and knee joint pain were evaluated by subjective judgment whether or not such factors created a hindrance during walking. Results: Among older adults without vision problems and knee joint pain that affected walking, those with superior knee extension strength had signifi cantly greater walking speed and step length than those with inferior knee extension strength (P <.05). Persons with visual acuity problems had higher cadence and shorter stance time. In addition, persons with pain in both knees showed slower walking speed and longer stance time and double support time. Conclusion: A decrease of knee extension strength and visual acuity and knee joint pain are factors affecting gait in the female older adults. Decreased knee extension strength and knee joint pain mainly affect respective distance and time parameters of the gait. © 2014 The Academy of Geriatric Physical Therapy of the American Physical Therapy Association. Unauthorized reproduction of this article is prohibited