Impulse Characteristics Research Articles

ANALYSIS OF SIMULATION DATA OF A SUPERSONIC FLOW IN A SHORT NOZZLE WITH A NOZZLE

In this paper, we analyzed the influence of the geometric parameters of a shortened nozzle when operating under various conditions - at sea level (at Р=1 bar) and upper atmosphere (Р= 0.1 bar). The influence of geometrical parameters of the nozzle, pressure at the inlet, and the environment on the impulse characteristics of the flow are considered. It is shown that the momentum factor decreases with decreasing inlet pressure, but with increasing flight altitude, i.e. a decrease in the pressure of the external environment, the momentum coefficient decreases to a certain value, and then increases again. This character of the dependence is explained by the wave structure of the flow in a shortened nozzle. The study of simulation data can be used to create new types of nozzles for rocket and space technology.

Psychometric properties of the Chinese version of the Quick Delay Questionnaire (C-QDQ) and ecological characteristics of reward-delay impulsivity of adults with ADHD

BackgroundThe Quick Delay Questionnaire (QDQ) is a short questionnaire designed to assess delay-related difficulties in adults. This study aimed to examine the reliability and validity of the Chinese version of the QDQ (C-QDQ) in Chinese adults, and explore the ecological characteristics of delay-related impulsivity in Chinese adults with attention-deficit/hyperactivity disorder (ADHD).MethodsData was collected from 302 adults, including ADHD (n = 209) and healthy controls (HCs) (n = 93). All participants completed the C-QDQ. The convergent validity, internal consistency, retest reliability and confirmatory factor analysis (CFA) of the C-QDQ were analyzed. The correlations between C-QDQ and two laboratory measures of delay-related difficulties and Barratt Impulsiveness Scale-11 (BIS-11), the comparison of C-QDQ scores between ADHD subgroups and HCs were also analyzed.ResultsThe Cronbach’s α of C-QDQ was between 0.83 and 0.89. The intraclass correlation coefficient of C-QDQ was between 0.80 and 0.83. The results of CFA of C-QDQ favoured the original two-factor model (delay aversion and delay discounting). Significant positive associations were found between C-QDQ scores and BIS-11 total score and performance on the laboratory measure of delay-related difficulties. Participants with ADHD had higher C-QDQ scores than HCs, and female ADHD reported higher scores on delay discounting subscale than male. ADHD-combined type (ADHD-C) reported higher scores on delay aversion subscale than ADHD-inattention type (ADHD-I).ConclusionThe C-QDQ is a valid and reliable tool to measure delay-related responses that appears to have clinical utility. It can present the delay-related impulsivity of patients with ADHD. Compared to HCs, the level of reward-delay impulsivity was higher in ADHD.

Symmetric circulant matrix decomposition-based multivariable group sparse coding for rolling bearing fault diagnosis

Singular value decomposition technique proves its effectiveness in mechanical signal analysis by decomposing the test signal into a series of singular spectral components of different frequency bands. Nevertheless, how to adapt this technology to the needs of cyclo-nonstationary signal and how to set the decomposition number while maintaining detailed features to obtain the optimal component containing the most fault information, remains an important issue that needs to be addressed in the field of mechanical fault diagnosis. To overcome these disadvantages, the symmetric circulant matrix decomposition (SCMD) is presented. Two main ideas structure the present technique. Firstly, symmetric circulant matrix is used to generate eigenvectors, which will better adapt to the cyclo-nonstationary signal associated with the structural symmetry of rotating machinery. Then, an impulse fluctuation measure is established to adaptively search for the decomposition number and extract the optimal component. Moreover, to better improve the impulse extraction effect of SCMD, the multivariate group sparse coding based on the multivariate correlation characteristics and intra group sparsity characteristics of impulse signals is proposed, which can enhance impulse features while preserving fault details as much as possible. The reliability and feasibility of the proposed method are verified by the experimental signals. The comparison with several classic methods shows that this method is more effectiveness in weak feature extraction.

Физически реализуемое восстановление непрерывного сигнала после дискретизации

It is proposed to describe signals in a physically realizable basis. Correlation functions of impulse characteristics of physically implemented filters are used as basic functions. To obtain analytical expressions of the functions of the proposed physically realizable basis, it is proposed to use inverse Fourier transforms from approximations (Butterworth, Chebyshev, etc.) of the squares of the amplitude-frequency characteristics of normalized low-pass filters. The basis, functions are copies of the indicated correlation functions of the impulse characteristics, shifted relative to each other by the same time interval, which is the sampling interval. It is shown that there is a sampling theorem in the space of the introduced functions. The exact restoration of the signal is possible if the functions of the considered basis have the property of readability. In this case, the considered basic functions are functions of counts and are not physically implemented. To reduce the error of restoring a continuous signal from its readings using the proposed basis, it is necessary to increase the order of the filter, the pulse characteristics of which are used in the formation of the basis. To restore a continuous signal, its samples must be fed to two cascaded filters. The first filter must have an impulse response, the correlation function of which is used to form a physically realizable basis. The second filter must be matched to the impulse response of the first filter.

Validation of numerical simulations and experiments on impulse characteristics induced by self-excited oscillation

The high-frequency pulse flow, equivalent to the natural frequency of rocks, is generated by a self-excited oscillating cavity to achieve resonance rock-breaking. The flow field and oscillating mechanism of the self-excited oscillating cavity were simulated using the large eddy simulation method of Computational Fluid Dynamics (CFD). A field-scale testing apparatus was developed to investigate the impulse characteristics and verify the simulation results. The results show that the fluid at the outlet at the tool is deflected due to the pulse oscillation of the fluid. The size and shape of low-pressure vortices constantly change, leading to periodic changes in fluid impedance within the oscillating cavity. The impulse frequency reaches its highest point when the length–diameter ratio is 0.67. As the length–diameter ratio increases, the tool pressure loss also increases. Regarding the cavity thickness, the impulse frequency of the oscillating cavity initially decreases, then increases, and finally decreases again. Moreover, both the impulse frequency and pressure loss increase with an increase in displacement. The numerical simulation findings align with the experimental results, thus confirming the validity of the theoretical model. This research provides theoretical guidance for the practical application of resonance rock-breaking technology.

Topological features of functional brain networks and subclinical impulsivity: an investigation in younger and older adults.

Impulsive traits (i.e., the tendency to act without forethought regardless of negative outcomes) are frequently found in healthy populations. When exposed to risk factors, individuals may develop debilitating disorders of impulse control (addiction, substance abuse, gambling) characterized by behavioral and cognitive deficits, eventually leading to huge socioeconomic costs. With the far-reaching aim of preventing the onset of impulsive disorders, it is relevant to investigate the topological organization of functional brain networks associated with impulsivity in sub-clinical populations. Taking advantage of the open-source LEMON dataset, we investigated the topological features of resting-state functional brain networks associated with impulsivity in younger (n=146, age: 20-35) and older (n=61, age: 59-77) individuals, using a graph-theoretical approach. Specifically, we computed indices of segregation and integration at the level of specific circuits and nodes known to be involved in impulsivity (frontal, limbic, and striatal networks). In younger individuals, results revealed that impulsivity was associated with a more widespread, less clustered and less efficient functional organization, at all levels of analyses and in all selected networks. Conversely, impulsivity in older individuals was associated with reduced integration and increased segregation of striatal regions. Speculatively, such alterations of functional brain networks might underlie behavioral and cognitive abnormalities associated with impulsivity, a working hypothesis worth being tested in future research. Lastly, differences between younger and older individuals might reflect the implementation of age-specific adaptive strategies, possibly accounting for observed differences in behavioral manifestations. Potential interpretations, limitations and implications are discussed.

Calculation Method for the Transient Hot-Spot Temperature Rise of Oil-Immersed Bushing in High-Speed Railway

Traction oil-immersed bushing is the only channel for connecting the high-speed railway system with the external power grid, and its transient hot spot is one of the most important factors reflecting its operation status. Since the traction load of a high-speed railway has obvious impulse characteristics, the existing calculation method for bushing given in IEEE Std C57.19-100™-2012 is incompatible because it is designed for steady electrical loads. Thus, in this paper, the equivalent hot spot temperature rise of the bushing under varying traction loads is calculated by the traction parameters (i.e., operating time <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_ot</i> , interval time <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_it</i> , and per unit transient traction current <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_tc</i> ). Then, the difference value of transient hot spot temperature rise is modified by analyzing the change of transient hot spot temperature rise under varying traction loads. Finally, a calculation method is proposed for the transient hot spot temperature rise of the oil-immersed bushing in high-speed railway under different traction loads. A case study of a 110 kV oil-immersed bushing shows that the proposed method is speedy and accurate.

Automotive tire facility noise characteristics

The environmental noise influence of facilities that change, replace or repair tires has notable acoustic characteristics, including the sound from air impact wrenches. Air impact wrenches are a ubiquitous tool at such facilities, where they are used to remove and replace the nuts that hold wheels on cars and trucks. The sound is commonly emitted through open doorways. Tire facility sound data was evaluated for impulsive characteristics using procedures described in the newest version of ISO 1996-3. The dynamic nature of air impact wrench sound also allowed the ISO 1996-3 approach to be evaluated.

Wave impact pressure and pressure impulse on a square column with an overhanging deck in regular waves

As the main component of semi-submersible platforms, the deck-column structure is inevitably subjected to severe wave impacts in extreme ocean environments. The wave impact pressure and its time integral, impact pressure impulse, play an important role in the structural design, especially for the analysis of dynamic response. To investigate the characteristics of impact pressure and pressure impulse, wave impact tests on a square column with overhanging deck were carried out under a series of regular waves. Wavelet denoising technique and empirical mode decomposition (EMD) method were employed to remove the noise interference and the dynamic amplification effect from raw data. Considering the stochastic feature, statistical analysis of pressure impulse was performed based on generalized extreme value (GEV) and two-parameter Weibull distribution models. The results show the strong variability of the wave pressure impulse and the necessity of statistical analysis even in regular waves. The peak impact pressure is more sensitive to the variation of initial air gap and column incline angle than the pressure impulse. The probability distribution of extreme pressure impulse agrees well with the GEV distribution and is mainly distinguished by the shape parameter. Furthermore, the probability distribution of extreme pressure impulse is significantly affected by the initial air gap, and the effect is also related to wave parameters. The present research reveals the probability distribution of wave pressure impulse in regular waves and lays a foundation for the statistical analysis of pressure impulse in irregular waves.

The effect of operating frequency and ignition energy on JP-10/PO/aluminum powder multiphase-pulse-detonation-engine

Pulse-Detonation-Engine is a new engine that uses pulse detonation wave to generate thrust. Previous studies have shown that JP-10/PO/Al dust multi-phase composite fuel has good ignition sensitivity and detonation strength, so the present work studies the application prospect of this optimized composite fuel in the detonation propulsion of Pulse-Detonation-Engine. A numerical model of Multiphase-Pulse-Detonation-Engine was established, and a high-precision Computational-Fluid-Dynamics simulation method was applied to study a series of cyclic processes such as multiphase fuel dispersion, ignition, detonation wave formation, and blowing during Multiphase-Pulse-Detonation-Engine operation. The effects of operating frequency (20–60 Hz) and ignition energy (25–400 J) on the flame acceleration law, thrust, and impulse characteristics in Multiphase-Pulse-Detonation-Engine were quantitatively discussed. The research results indicate that the propulsion effect produced by single-cycle Multiphase-Pulse-Detonation-Engine deteriorates as the operating frequency increases. On the other hand, as the number of operating cycles per unit time increases, the fuel specific impulse gradually increases. But the increase rate gradually decreases, and the operating frequency should not exceed 50 Hz under current inspection conditions. The ignition energy has a promoting effect on the early flame acceleration of multiphase explosions. Due to the cumulative effect of multiple cycles, the impact of ignition energy on the propulsion performance of continuous working Multiphase-Pulse-Detonation-Engine is more significant, with ignition energy increasing from 25 J to 400 J, and specific impulse increasing by approximately 18.3 %.

Method for Estimating Road Impulse Ahead of Vehicles in Urban Environment with Microelectromechanical System Three-Dimensional Sensor.

Most automated vehicles (AVs) are equipped with abundant sensors, which enable AVs to improve ride comfort by sensing road elevation, such as speed bumps. This paper proposes a method for estimating the road impulse features ahead of vehicles in urban environments with microelectromechanical system (MEMS) light detection and ranging (LiDAR). The proposed method deploys a real-time estimation of the vehicle pose to solve the problem of sparse sampling of the LiDAR. Considering the LiDAR error model, the proposed method builds the grid height measurement model by maximum likelihood estimation. Moreover, it incorporates height measurements with the LiDAR error model by the Kalman filter and introduces motion uncertainty to form an elevation weight method by confidence eclipse. In addition, a gate strategy based on the Mahalanobis distance is integrated to handle the sharp changes in elevation. The proposed method is tested in the urban environment. The results demonstrate the effectiveness of our method.

A study of the interactive mediating effect of ADHD and NSSI caused by co-disease mechanisms in males and females.

Non-suicidal self-injury (NSSI), of which the predisposing factors are complex and diverse, profoundly affects the physical and mental health of young people. Therefore, this work established an NSSI intermediary network model considering the interaction of multiple factors. A mediating effect between attention-deficit/hyperactivity disorder (ADHD) and NSSI, considering the influence of comorbidities, such as depression, anxiety, and impulsive personality, was proposed based on sex differences. A total of 2,689 middle school students in Ningbo City, Zhejiang Province, China, were randomly sampled and participated in this study. Data regarding their demographic characteristics, attention deficit, hyperactivity/impulsivity, NSSI, anxiety, depression, internet addiction, and other comorbid symptoms were collected and analyzed. After initially screening the data, variables were assessed for significance using a single-factor inter-group difference analytic method, and a binary logistic regression analysis was performed. The intermediary effect of factors influencing NSSI in males and females was also analyzed. The overall NSSI rate was 15.16%. The results showed that the impact of individual impulsivity characteristics (impulsiveness, the ADHD with hyperactivity/impulsivity subtype) on NSSI behavior was not significant (regression results, P>0.05). The degree of association between ADHD with attention deficit and ADHD with comprehension deficit subtypes, and other comorbid symptoms (depression, anxiety, and internet addiction disorder) and NSSI, with odds ratios (ORs) of 7.6/6.42/436.68/3.82/1.86, and 95% bootstrap confidence intervals (CIs) of 4.64, 12.87/3.46, 12.67/137.42, 2659.13/2.32, 6.37/1.31, 2.82, respectively. The results also showed significant effects of ADHD subtypes on comorbid symptoms and the path effects of NSSI (P<0.01). Among them, the mediating effect was the strongest when anxiety was the mediating variable, and the mediating effect of girls was higher than that of boys. The results of this work demonstrated the influence of ADHD symptoms on NSSI behavior. Among patients with ADHD, patients with subtypes with obvious attention deficit characteristics were more likely to exhibit NSSI behavior, whereas the hyperactive impulse subtype had no direct impact on NSSI. We conclude that adolescent impulsivity may not be directly related to NSSI behavior and that impulsive characteristics jointly affect NSSI behavior through a series of NSSI comorbid symptoms. Notably, the probability of symptom onset and the degree of comorbidity was significantly higher in girls than in boys of the same age, and girls were more prone to NSSI behavior. These findings provide effective theoretical support for the prevention and treatment of adolescent NSSI behavior.

An adaptive enhanced envelope spectrum technique for bearing fault detection in conditions characterized by strong noise

Rolling bearings are widely used in rotating machinery and have a high failure rate. Regrettably, the task of ensuring dependable bearing fault detection presents a formidable challenge, especially when the bearing fault-related characteristics are non-stationary or even affected by strong noise. In response to this challenge, a novel adaptive enhanced envelope spectrum (AEES) technique is proposed in this study. Firstly, it generates representative intrinsic mode functions (IMFs) using the variational mode decomposition algorithm. Then, based on the analysis of the envelope spectrum normalized mutual information and time-domain fuzzy entropy, a new IMF selection and integration strategy combining time- and frequency-domain metrics is suggested to reconstruct the most informative analytical signal. An adaptive filter is employed to post-process the reconfigured signal to reinforce fault-related impulsive characteristics, the optimal length of which is ascertained through the proposed variable step-size search technique based on unbiased autocorrelation analysis. The efficacy of the AEES technique has been validated through a sequence of experiments conducted under diverse bearing conditions. Its robustness and distinct advantages under strong noise conditions are tested using a publicly available dataset. The validation results show that the AEES technique can effectively identify the health conditions of bearings under high noise conditions (signal-to-noise ratios between 1 dB and 3 dB). Compared with two relevant techniques in the existing literature and a classical method, the proposed AEES technique can achieve signal processing results with fewer interference components and more prominent characteristic frequency information and has a unique ability to identify fault features in some challenging situations.

Experimental study on the discharge of a xenon-assisted krypton Hall thruster

The theoretical specific impulse of Hall thrusters using a krypton propellant is much higher than that of those using xenon. However, the actual benefits of this improvement are limited by the difficulty in achieving krypton atom ionization, and its efficiency is much lower than that of xenon. In this study, the anode specific impulse and anode efficiency of Hall thrusters using krypton propellant were improved by adding a small quantity of xenon. A dual-channel supply of xenon and krypton was achieved by optimizing the discharge channel structure based on the design of the aft-loaded magnetic field. The effects of the xenon and krypton supply method and xenon fraction on the discharge characteristics of the Hall thruster were investigated by conducting discharge experiments using the mixed propellant. The results indicated that injecting a small quantity of xenon significantly improved the ionization of krypton, improved the ionization and acceleration efficiency of the thruster, and fully utilized the high specific impulse characteristics of krypton. Furthermore, the addition of a small quantity of xenon also significantly increased the upper limit of the discharge voltage for stable operation using krypton from 500 V. At the maximum tested xenon fraction, the maximum discharge voltage was loaded to 900 V. At a discharge voltage of 800 V, the optimal anode efficiency and anode specific impulse increased by 4.5 % and 534 s, respectively, compared with those for pure xenon propellant (with an anode efficiency of 54 % and anode specific impulse of 3034 s). The results of this study are of great significance for the design of high-efficiency, high-specific-impulse, and low-cost Hall thrusters.

Impulsivity in adolescent girls diagnosed with trichotillomania: an evaluation of clinical and neuropsychological characteristics

The aim of this study is to compare the clinical and neuropsychological features of impulsivity in adolescent girls with trichotillomania (TTM) and healthy controls, and to assess the relationships between the severity of TTM and the impulsivity/concomitant symptoms of anxiety and depression. The study sample consisted of 43 adolescent girls who were 12 to 18 years old. The Kiddie-Schedule for Affective Disorders and Schizophrenia for School Age Children-Present and Lifetime Version DSM-5 (K-SADS-PL) was administered to the adolescents and their parents. All of the participants completed a sociodemographic data form, the Revised Children’s Anxiety and Depression Scale-Child Version (RCADS-CV), the Barratt Impulsiveness Scale-Brief (BIS-Brief), and the Massachusetts General Hospital Hairpulling Scale (MGH-HPS). The Eriksen Flanker task, the Stop Signal Reaction Time (SSRT) task, the Go/No-Go task, and the Balloon Analog Risk Task (BART) were used to assess behavioral impulsivity. The adolescents with TTM reported higher levels of impulsivity and anxiety/depression symptoms than the healthy controls, and they also performed worse on the behavioral tasks. While there were no relationships between clinical and behavioral impulsivity and TTM severity, social anxiety symptoms were the most important predictor of the severity of TTM. It seems important to better understand the role of impulsivity in the onset and persistence of TTM symptoms in adolescents.

Impulse Characteristics of Soil Treated with Enhancement Materials and Various Moisture Contents

Due to the high mineral contents of additives and enhancement materials (EMs), EMs have become popular in treating soil, which expectedly improves the electrical characteristics of soil. Much of the published work on the effectiveness of EMs is based on investigations at low magnitudes of voltage, current and frequency; however, the study of these EMs under high-impulse conditions has not been widely addressed. In this work, the experimental results of a small-mesh ground electrode without EMs and treated with EMs, where the latter was poured with a controlled amount of water, are presented. The impulse impedance was expected to change appreciably due to the ionic conduction in soil and the use of EMs with a high water content; however, the impulse impedance was found to be weak and dependent on the water content, and the inductive effect was found to be significant at the voltage and current decay times. This indicates that, even though EMs and highly wetted soil can reduce the soil resistivity and relative resistance value, special attention has to be given to the impulse characteristics of the ground electrodes, particularly at tail/decay times.

The Effects of Selective Serotonin Reuptake Inhibitors on Impulsivity in Young Adults with Major Depression in the Early Phase of Treatment.

Whether selective serotonin reuptake inhibitors (SSRI) increase suicide risk, especially in young adults, is still a controversial issue. This study aimed to examine the change in impulsivity characteristics and to evaluate the relationship between impulsivity and suicidality in young adults with major depression who were started on SSRIs. The study included 50 patients between the ages of 18-24 years with a diagnosis of major depression who were planned to start SSRIs. Participants were evaluated with the Beck Depression Scale, Beck Anxiety Scale, Young Mania Rating Scale, Columbia Suicide Severity Rating Scale, Barratt Impulsivity Scale, Daily Impulsivity Scale (DIS), and Go/ No-Go Task (GNG) before and at the end of the first week of treatment. Seventy percent of the patients (n: 35) completed the assessments at baseline and at the end of the first week. At the end of one-week there was a statistically significant decrease in the DIS (t=2.283, p=0.029) and commission errors in GNG (t=3.19, p=0.003). In addition, 7 out of 11 patients who had suicidal ideation at the first evaluation did not continue to have suicidal ideation at the end of the first week and there was a significant decrease in the severity of suicidal ideation at the end of the follow-up (W:132.0, p<0.001). One-week SSRI use in young adults resulted in a decrease in impulsivity in self-report scales assessing state impulsivity and in the GNG. It was observed that the severity of suicidal ideation decreased at the end of the one-week treatment period.

자애(Metta)명상과 ADHD 청소년의 또래 관계 개선에 관한 연관성 연구

This paper is a study that revealed that Metta meditation helps improve peer relationships among young people with ADHD (Attention Deficit Hyperactivity Disorder). I hope that young people living with ADHD symptoms can recognize differences in viewpoints of people around them with a negative perspective, recognize differences for themselves through psychological and emotional stability by combining medication and Buddhist meditation to solve external problems, and they will live a happy life as a member of society by improving their self-esteem and developing interpersonal skills by utilizing their strengths and weaknesses with people around them. &#x0D; Its purpose is to find out how Buddhist meditation can influence healing in ADHD adolescents in relation to peer relationships. Countries, local communities, and private institutions are studying various methods and establishing new organizations to try to solve problems. But It seems difficult to find a fundamental solution. Therefore, this study aims to approach solutions for young people with ADHD through Buddhist meditation from a Buddhist perspective.&#x0D; In this article, I first examined the theoretical background of improving peer relationships and Metta meditation, and considered Metta meditation. We also discussed whether there is a possibility of improving peer relationships among young people with ADHD. Metta meditation is a literature review that reveals that emotional composure has the opposite effect of improving interpersonal skills due to excellent coping ability.&#x0D; Through this study, it has been revealed that adolescents with ADHD are immature in interaction in peer relationships due to lack of performance in social skills due to lack of attention deficit hyperactivity, and impulsiveness characteristics. Also, adolescents with they have difficulty controlling their emotions and have a tendency to be less responsive to questions than efficiently communicating information. On the other hand, it has been proven that charity meditation stimulates the right brain, activates parasympathetic nerves, increases endorphins in the brain, and is effective in improving peer relationships with positive emotions. Through Metta meditation, ADHD adolescents can look forward to the effect of developing personal resources and helping them resolve conflicts in relationships with peers or people around them by looking at their minds.

Study on the Sand-Scouring Characteristics of Pulsed Submerged Jets Based on Experiments and Numerical Methods

Water-jet-scouring technology finds extensive applications in various fields, including marine engineering. In this study, the pulse characteristics are introduced on the basis of jet-scouring research, and the sand-scouring characteristics of a pulsed jet under different Reynolds numbers and the impact distances are deeply investigated using Flow-3D v11.2. The primary emphasis is on the comprehensive analysis of the unsteady flow structure within the scouring process, the impulse characteristics, and the geometric properties of the resulting scouring pit. The results show that both the radius and depth of the scour pit show a good linear correlation with the jet-flow rate. The concentration of suspended sediment showed an increasing and then decreasing trend with impinging distance. The study not only helps to enrich the traditional theory of jet scouring, but also provides useful guidance for engineering applications, which have certain theoretical and practical significance.

Disorders of impulsivity in trichotillomania and skin picking disorder

Trichotillomania and skin picking disorder are often classified as body-focused repetitive behaviors (BFRBs) as they are characterized by repetitive hair-pulling and skin picking, respectively. They were initially considered to be impulse control disorders despite little research scrutiny. The objective of this study was to examine the relationship of these two conditions to other disorders with impulsive features. Adults with trichotillomania (n = 104) and skin picking (n = 178) or both (n = 96) were recruited from the general community using advertisements and online support groups and completed an online survey. Participants undertook a structured clinical interview and completion of self-report instruments to characterize clinical profiles and associated characteristics. In addition, each participant completed the Minnesota Impulse Disorders Interview to screen for disorders with impulsive features. Of the 378 adults with BFRBs, 134 (35.4%) screened positive for at least one disorder with features of impulsivity with the most common being compulsive buying (18.3%) and problematic use of the internet (17.5%). Participants with a co-occurring disorder of impulsivity reported significantly worse pulling and picking symptoms (p < .001), were more likely to have co-occurring alcohol problems (p < .001) and PTSD (p < .001), and scored higher regarding dissociative symptoms (p < .001). BFRBs are associated with a range of impulsive disorders and the comorbidity may have important treatment implications.